Birth Island Deoxys .

Using the Aurora Ticket received from events on their GameBoy Advance retail copy of Pokémon FireRed & LeafGreen games,
players gain access to the Birth Island, and get a chance to capture the Mythical Deoxys!

Do note that the Aurora Ticket was never distributed to the Japanese GBA copies of Pokémon Emerald Version.

Starting February 27th 2026, players can purchase the Virtual Console copies for Pokémon FireRed & LeafGreen on the Switch and Switch 2. 
After defeating the Elite 4, the event ticket (and enabling of required flags) will be automatically added into the player's save by the game.
 

For GBA players who rather not use the Mystery Gift to activate the event, simply use PKHeX's Event Flags > Research, and
For Pokémon FireRed & LeafGreen: Check Flag 2122 and Flag 2123 , then proceed to add an Aurora Ticket into the Key Items of the Bag.

For Pokémon FireRed & LeafGreen, having the National Dex and Rainbow Pass may be required. More event flags here.