theSLAYER

Species   Mesprit   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Nameless Cavern   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Levitate   Item   None    Moves   (ITALIC means Relearnable)   Lucky Chant   Future Sight   Charm   Extrasensory
  Format Ver.1.0.6-2, Post Updated Date:20180506_0536

Species   Azelf   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Nameless Cavern   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Levitate   Item   None    Moves   (ITALIC means Relearnable)   Uproar   Future Sight   Nasty Plot   Extrasensory
  Format Ver.1.0.6-2, Post Updated Date:20180506_0534

In Pokemon Omega Ruby & Alpha Sapphire, after players complete the puzzle at the Sealed Chamber, the entrances to Desert Ruins, Island Cave and Ancient Tomb will become unsealed.

In order to encounter Regigigas, the player has to bring Regirock, Registeel and Regice to the Island Cave, in daytime.
Additionally, the Regice has to be nicknamed, and must carry an frozen-affiliated item, namely CasteliaCone, Snowball, or Never-Melt Ice.
     Species   Regigigas   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Island Cave   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Slow Start   Item   None    Moves   (ITALIC means Relearnable)   Foresight   Revenge   Wide Guard   Zen Headbutt
  Format Ver.1.0.6-2, Post Updated Date:20180505_2221

After players complete the puzzle at the Sealed Chamber, the entrances to Desert Ruins, Island Cave and Ancient Tomb will become unsealed.
After entering the chamber, another puzzle will come between the player and the golem residing within.
In order to gain access to the rear chamber, the player has to read the Braille on the wall,
then proceed to the center of the room and have a Pokemon in the party use Fly (HM).
     Species   Registeel   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Ancient Tomb   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 40    Nature   Random   Ability   Clear Body   Item   None    Moves   (ITALIC means Relearnable)   Curse   Ancient Power   Iron Defense   Amnesia
  Format Ver.1.0.6-2, Post Updated Date:20180505_2215

After players complete the puzzle at the Sealed Chamber, the entrances to Desert Ruins, Island Cave and Ancient Tomb will become unsealed.
After entering the chamber, another puzzle will come between the player and the golem residing within.
In order to gain access to the rear chamber, the player has to read the Braille on the wall,
Use the D-pad to go right twice, and go down twice, and finally have a Pokemon in the party use Strength (HM).
     Species   Regirock   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Desert Ruins   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 40    Nature   Random   Ability   Clear Body   Item   None    Moves   (ITALIC means Relearnable)   Bulldoze   Curse   Ancient Power   Iron Defense
  Format Ver.1.0.6-2, Post Updated Date:20180505_2213

After players complete the puzzle at the Sealed Chamber, the entrances to Desert Ruins, Island Cave and Ancient Tomb will become unsealed.
After entering the chamber, another puzzle will come between the player and the golem residing within.
In order to gain access to the rear chamber, the player has to read the Braille on the wall, and wait a full 2 minutes.
     Species   Regice   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Island Cave   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 40    Nature   Random   Ability   Clear Body   Item   None    Moves   (ITALIC means Relearnable)   Bulldoze   Curse   Ancient Power   Amnesia
  Format Ver.1.0.6-2, Post Updated Date:20180505_2209

In Pokemon Omega Ruby & Alpha Sapphire, after main storyline involving the Primal Groudon or Primal Kyogre,
Heatran can be found in the hoop portal at the end of cave.
     Species   Heatran   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Scorched Slab   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Flash Fire   Item   None    Moves   (ITALIC means Relearnable)   Metal Sound   Crunch   Scary Face   Lava Plume
  Format Ver.1.0.6-2, Post Updated Date:20180505_2125

Original Creator
@suloku
 
XY friend safari usage
To be added
 
ORAS Mirage Island usage
This tool works by adding the wanted Mirage Spots to the PSS Passerby data.
Unlike standard daily mirage spots, players will not be able to access the hidden items.

However with this tool, players will be able to reach Crescent Isle much easily, to encounter Cresselia.

In order for this tool to work:
1. Make a fresh save for the day (Save in-game for that day, before you continue)
2. Use PKHeX to set the Player's Trainer ID to 00000,
3. Use this tool to set the ID of the islet you wanted.
4. Must remain as TID 00000 when soaring in the sky.
5. Land on the intend islet.
6. Save the game
7. You may now switch back to your previous TID
 
Original Research Thread
Research done covered Teleportation coordinates to the islands, and StreetPass Passerby Data for Mirage spots:

In Pokemon Omega Ruby & Alpha Sapphire, the Crescent Isle is one of out the thirty three daily random mirage spots that may appear.
It is possible to receive another 10 mirage spots from StreetPass, and it is possible to receive this mirage spot using this method.
     Species   Cresselia   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Crescent Isle   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Levitate   Item   None    Moves   (ITALIC means Relearnable)   Mist   Aurora Beam   Future Sight   Slash
  Format Ver.1.0.6-2, Post Updated Date:20180505_2019

In Pokemon Omega Ruby & Alpha Sapphire, when the player is soaring in the sky with 3 maxed effort values Pokemon in their party, the Pathless Plain mirage spot will appear.
When the player interacts with the hoop towards the end of the Pathless Plain, a battle will be initiated.
Virizion can be encountered on Mondays and Thursdays, Terrakion can be encountered on Tuesdays and Saturdays, and Cobalion can be encountered on Wednesdays, Fridays and Sundays.
     Species   Virizion   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Pathless Plain   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Justified   Item   None    Moves   (ITALIC means Relearnable)   Retaliate   Giga Drain   Sacred Sword   Swords Dance
  Format Ver.1.0.6-2, Post Updated Date:20180505_2016

In Pokemon Omega Ruby & Alpha Sapphire, when the player is soaring in the sky with 3 maxed effort values Pokemon in their party, the Pathless Plain mirage spot will appear.
When the player interacts with the hoop towards the end of the Pathless Plain, a battle will be initiated.
Virizion can be encountered on Mondays and Thursdays, Terrakion can be encountered on Tuesdays and Saturdays, and Cobalion can be encountered on Wednesdays, Fridays and Sundays.
     Species   Terrakion   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Pathless Plain   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Justified   Item   None    Moves   (ITALIC means Relearnable)   Retaliate   Rock Slide   Sacred Sword   Swords Dance
  Format Ver.1.0.6-2, Post Updated Date:20180505_2010

In Pokemon Omega Ruby & Alpha Sapphire, when the player is soaring in the sky with 3 maxed effort values Pokemon in their party, the Pathless Plain mirage spot will appear.
When the player interacts with the hoop towards the end of the Pathless Plain, a battle will be initiated.
Virizion can be encountered on Mondays and Thursdays, Terrakion can be encountered on Tuesdays and Saturdays, and Cobalion can be encountered on Wednesdays, Fridays and Sundays.
     Species   Cobalion   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Pathless Plain   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Justified   Item   None    Moves   (ITALIC means Relearnable)   Retaliate   Iron Head   Sacred Sword   Swords Dance
  Format Ver.1.0.6-2, Post Updated Date:20180505_2002

In Pokemon Omega Ruby & Alpha Sapphire, after the player defeats the Elite Four for the first time, the player is able to complete the post-game quest: Delta Episode.
The final act of the arc, the player has to capture Rayquaza, and ride Mega Rayquaza into space, with the aim to destroy a meteorite that is hurdling down to Earth, threatening to decimate the Hoenn region.
This Pokemon has to be captured, in order to progress through the storyline.
If it was defeated or ran from, it would still be there, awaiting the player to begin the encounter again.
Additionally, even if the player attempts to fill all the slots in their PC, Box 31 was hidden from usage,
and is only unlocked after this Pokemon's capture.
     Species   Rayquaza   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Sky Pillar   Dates   (Various)   PID   Cannot Be Shiny   Games   ORAS                                                                Lv. 70    Nature   Random   Ability   Air Lock   Item   None    Moves   (ITALIC means Relearnable)   Extreme Speed   Dragon Pulse   Dragon Dance   Dragon Ascent
  Format Ver.1.0.6-2, Post Updated Date:20180504_2055

In Pokemon Alpha Sapphire, when the player is soaring in the sky with a Level 100 Pokemon in their party,
the Fabled Cave mirage spot will appear.

When the player interacts with the hoop in the Fabled Cave, Zekrom will appear.
This also marks the first time Zekrom being able to be encountered shiny.
     Species   Zekrom   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Fabled Cave   Dates   (Various)   PID   Chance of Shiny   Games   AS                                                                Lv. 50    Nature   Random   Ability   Teravolt   Item   None    Moves   (ITALIC means Relearnable)   Dragon Breath   Slash   Zen Headbutt   Fusion Bolt
  Format Ver.1.0.6-2, Post Updated Date:20180504_1957

In Pokemon Omega Ruby & Alpha Sapphire, when the player is soaring in the sky with Dialga and Palkia in their party,
a rift in space-time will appear over Hoenn.
When the player interacts with the rift, Giratina is encountered.
     Species   Giratina   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Soaring in the sky   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Pressure   Item   None    Moves   (ITALIC means Relearnable)   Aura Sphere   Shadow Claw   Shadow Force   Hex
  Format Ver.1.0.6-2, Post Updated Date:20180504_1955

In Pokemon Alpha Sapphire, when the player is soaring in the sky with Azelf, Mesprit and Uxie in their party,
a rift in space-time will appear over Hoenn.
When the player interacts with the rift, Dialga is encountered.
     Species   Dialga   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Soaring in the sky   Dates   (Various)   PID   Chance of Shiny   Games   AS                                                                Lv. 50    Nature   Random   Ability   Pressure   Item   None    Moves   (ITALIC means Relearnable)   Aura Sphere   Iron Tail   Roar of Time   Flash Cannon
  Format Ver.1.0.6-2, Post Updated Date:20180504_1951

In Pokemon Alpha Sapphire, after main storyline involving the Primal Kyogre, the player will receive the Tidal Bell key item after speaking to Captain Stern in Slateport City.
Players can then head to the Sea Mauville to encounter Lugia.
     Species   Lugia   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Sea Mauville   Dates   (Various)   PID   Chance of Shiny   Games   AS                                                                Lv. 50    Nature   Random   Ability   Pressure   Item   None    Moves   (ITALIC means Relearnable)   Rain Dance   Hydro Pump   Aeroblast   Punishment
  Format Ver.1.0.6-2, Post Updated Date:20180504_1936

The Trackless Forest is a mirage spot that appears when the player is soaring in the sky, with Lugia or Ho-Oh in their party.
     Species   Suicune   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Trackless Forest   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Pressure   Item   None    Moves   (ITALIC means Relearnable)   Aurora Beam   Mist   Mirror Coat   Ice Fang
  Format Ver.1.0.6-2, Post Updated Date:20180504_1931

The Trackless Forest is a mirage spot that appears when the player is soaring in the sky, with Lugia or Ho-Oh in their party.
     Species   Entei   Nickname   (default, save lang)   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Trackless Forest   Dates   (Various)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Pressure   Item   None    Moves   (ITALIC means Relearnable)   Stomp   Flamethrower   Swagger   Fire Fang
  Format Ver.1.0.6-2, Post Updated Date:20180504_1929

Species   Spiritomb   Nickname   (default, in )   OT   (recipient)   TID   (recipient)   Distribution   In-Game Encounter   Location   Sea Mauville   Dates   (Various Dates)   PID   Chance of Shiny   Games   ORAS                                                                Lv. 50    Nature   Random   Ability   Pressure   Item   Smoke Ball    Moves   (ITALIC means Relearnable)   Sucker Punch   Nasty Plot   Memento   Dark Pulse
  Format Ver.1.0.6-2, Post Updated Date:20180503_2211

This event was given away to commemorate The Year of Legendary Pokémon via Serial Code.
The gift received between Pokémon Sun & Moon and Pokémon Ultra Sun & Ultra Moon will slightly differ, in areas such as held item, level and moveset.

This Xerneas can only be received on Pokémon Moon & Ultra Moon, contrasting the fact that it is normally able to be encountered in the Ultra Space Wilds of Pokémon Ultra Sun.
     Species   Xerneas   Nickname   (default, save lang)   OT   Legenden2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: M                                                                Lv. 60    Nature   Random   Ability   Fairy Aura (1)   Item   None   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Geomancy   Horn Leech   Night Slash   Moonblast   WC ID 650: 「Xerneas glänzt im Kampf!」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Xerneas glänzt im Kampf! Xerneas, das Legendäre Pokémon vom Typ Fee,
ist bereit, majestätisch in den Kampf zu schreiten.
Setze seine einzigartige Attacke Geokontrolle ein,
um mehrere Statuswerte stark zu erhöhen! Format Ver.1.0.6-2, Post Updated Date:20180503_0200
     Species   Xerneas   Nickname   (default, save lang)   OT   Legenden2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: UM                                                                Lv. 100    Nature   Random   Ability   Fairy Aura (1)   Item   Gold Bottle Cap   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Geomancy   Focus Blast   Grass Knot   Moonblast   WC ID 650: 「Xerneas glänzt im Kampf!」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Xerneas glänzt im Kampf! Xerneas, das Legendäre Pokémon vom Typ Fee,
ist bereit, majestätisch in den Kampf zu schreiten.
Setze seine einzigartige Attacke Geokontrolle ein,
um mehrere Statuswerte stark zu erhöhen! Format Ver.1.0.6-2, Post Updated Date:20180503_0201

This event was given away to commemorate The Year of Legendary Pokémon via Serial Code.
The gift received between Pokémon Sun & Moon and Pokémon Ultra Sun & Ultra Moon will slightly differ, in areas such as held item, level and moveset.

This Yveltal can only be received on Pokémon Sun & Ultra Sun, contrasting the fact that it is normally able to be encountered in the Ultra Space Wilds of Pokémon Ultra Moon.
     Species   Yveltal   Nickname   (default, save lang)   OT   Leyendas2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   US & EU 3DS: S                                                                Lv. 60    Nature   Random   Ability   Dark Aura (1)   Item   None   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Oblivion Wing   Dark Pulse   Phantom Force   Psychic   WC ID 650: 「¡Un Yveltal sombrío!」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic ¡Un Yveltal sombrío! La oscuridad precede al misterioso Pokémon
legendario Yveltal, capaz de envolver en tinieblas
a sus oponentes con sus abrumadores ataques
Ala Mortífera y Pulso Umbrío. Format Ver.1.0.6-2, Post Updated Date:20180503_0213
     Species   Yveltal   Nickname   (default, save lang)   OT   Leyendas2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   US & EU 3DS: US                                                                Lv. 100    Nature   Random   Ability   Dark Aura (1)   Item   Gold Bottle Cap   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Oblivion Wing   Dark Pulse   Heat Wave   Tailwind   WC ID 650: 「¡Un Yveltal sombrío!」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic ¡Un Yveltal sombrío! La oscuridad precede al misterioso Pokémon
legendario Yveltal, capaz de envolver en tinieblas
a sus oponentes con sus abrumadores ataques
Ala Mortífera y Pulso Umbrío. Format Ver.1.0.6-2, Post Updated Date:20180503_0214

This event was given away to commemorate The Year of Legendary Pokémon via Serial Code.
The gift received between Pokémon Sun & Moon and Pokémon Ultra Sun & Ultra Moon will slightly differ, in areas such as held item, level and moveset.

This Yveltal can only be received on Pokémon Sun & Ultra Sun, contrasting the fact that it is normally able to be encountered in the Ultra Space Wilds of Pokémon Ultra Moon.
     Species   Yveltal   Nickname   (default, save lang)   OT   Leggende2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: S                                                                Lv. 60    Nature   Random   Ability   Dark Aura (1)   Item   None   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Oblivion Wing   Dark Pulse   Phantom Force   Psychic   WC ID 650: 「Il tenebroso Yveltal」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Il tenebroso Yveltal Il Pokémon leggendario Yveltal
fa piombare l'oscurità
ovunque al suo passaggio!
Con le sue mosse formidabili
Ali del Fato e Neropulsar, oscurerà
ogni barlume di speranza del nemico! Format Ver.1.0.6-2, Post Updated Date:20180503_0209
     Species   Yveltal   Nickname   (default, save lang)   OT   Leggende2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: US                                                                Lv. 100    Nature   Random   Ability   Dark Aura (1)   Item   Gold Bottle Cap   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Oblivion Wing   Dark Pulse   Heat Wave   Tailwind   WC ID 650: 「Il tenebroso Yveltal」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Il tenebroso Yveltal Il Pokémon leggendario Yveltal
fa piombare l'oscurità
ovunque al suo passaggio!
Con le sue mosse formidabili
Ali del Fato e Neropulsar, oscurerà
ogni barlume di speranza del nemico! Format Ver.1.0.6-2, Post Updated Date:20180503_0210

This event was given away to commemorate The Year of Legendary Pokémon via Serial Code.
The gift received between Pokémon Sun & Moon and Pokémon Ultra Sun & Ultra Moon will slightly differ, in areas such as held item, level and moveset.

This Xerneas can only be received on Pokémon Moon & Ultra Moon, contrasting the fact that it is normally able to be encountered in the Ultra Space Wilds of Pokémon Ultra Sun.
     Species   Xerneas   Nickname   (default, save lang)   OT   Leggende2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: M                                                                Lv. 60    Nature   Random   Ability   Fairy Aura (1)   Item   None   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Geomancy   Horn Leech   Night Slash   Moonblast   WC ID 650: 「Il radioso Xerneas」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Il radioso Xerneas Il Pokémon leggendario di tipo Folletto
Xerneas è pronto per il suo grandioso
ingresso nella lotta. Sfrutta la sua mossa
esclusiva Geocontrollo per aumentare
i valori di varie sue statistiche! Format Ver.1.0.6-2, Post Updated Date:20180503_0207
     Species   Xerneas   Nickname   (default, save lang)   OT   Leggende2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: UM                                                                Lv. 100    Nature   Random   Ability   Fairy Aura (1)   Item   Gold Bottle Cap   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Geomancy   Focus Blast   Grass Knot   Moonblast   WC ID 650: 「Il radioso Xerneas」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Il radioso Xerneas Il Pokémon leggendario di tipo Folletto
Xerneas è pronto per il suo grandioso
ingresso nella lotta. Sfrutta la sua mossa
esclusiva Geocontrollo per aumentare
i valori di varie sue statistiche! Format Ver.1.0.6-2, Post Updated Date:20180503_0208

This event was given away to commemorate The Year of Legendary Pokémon via Serial Code.
The gift received between Pokémon Sun & Moon and Pokémon Ultra Sun & Ultra Moon will slightly differ, in areas such as held item, level and moveset.

This Yveltal can only be received on Pokémon Sun & Ultra Sun, contrasting the fact that it is normally able to be encountered in the Ultra Space Wilds of Pokémon Ultra Moon.
     Species   Yveltal   Nickname   (default, save lang)   OT   Legenden2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: S                                                                Lv. 60    Nature   Random   Ability   Dark Aura (1)   Item   None   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Oblivion Wing   Dark Pulse   Phantom Force   Psychic   WC ID 650: 「Yveltal wirft seinen Schatten!」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Yveltal wirft seinen Schatten! Dunkelheit folgt dem geheimnisvollen
Legendären Pokémon Yveltal auf dem Fuß!
Mit seinen überwältigenden Attacken
Unheilsschwingen und Finsteraura sorgt es dafür,
dass seinen Gegnern schwarz vor Augen wird! Format Ver.1.0.6-2, Post Updated Date:20180503_0205
     Species   Yveltal   Nickname   (default, save lang)   OT   Legenden2018   TID   050418   Distribution   Serial Code   Location   a lovely place   Dates   May 04 to Aug 28, 2018   PID   Cannot Be Shiny   Games   EU 3DS: US                                                                Lv. 100    Nature   Random   Ability   Dark Aura (1)   Item   Gold Bottle Cap   Bundled Item   None   Card Per Save   Only One Allowed    Moves   (ITALIC means Relearnable)   Oblivion Wing   Dark Pulse   Heat Wave   Tailwind   WC ID 650: 「Yveltal wirft seinen Schatten!」's receiving text 0x2C Thank you for playing Pokémon! Please pick up your gift from the deliveryman in any Pokémon Center.

Classic Yveltal wirft seinen Schatten! Dunkelheit folgt dem geheimnisvollen
Legendären Pokémon Yveltal auf dem Fuß!
Mit seinen überwältigenden Attacken
Unheilsschwingen und Finsteraura sorgt es dafür,
dass seinen Gegnern schwarz vor Augen wird! Format Ver.1.0.6-2, Post Updated Date:20180503_0206