[Proof of Concept] Infinite Rare Candy in Sword/Shield

[Matroskin]

Proof of Concept: Infinite Rare Candy Works in Sword/Shield

TL;DR

Infinite Rare Candy is possible in Sword/Shield.

Not as a fake stack of 999 candies. Not as a renamed item that only half-works. A reusable Key Item can be routed into the real Rare Candy behavior, protected from consumption, made stable in the bag UI, and optionally tied to custom progression-based level caps.

This proof of concept was found while modding for my upcoming mod, Pokémon Royal Sword, and was inspired by Pokémon Run & Bun’s approach to cutting out unnecessary grinding while keeping the actual challenge focused on battles, routing, and team building.

The item can be configured during install in two major ways:

As a purely infinite Rare Candy-style item.
As an infinite item that only levels Pokémon up to custom progression-based level caps.

Those level caps can be tied to story completion flags/work values triggered by major trainer battles, such as rivals, Gym Leaders, and other progression milestones.

One important limitation: because the item is added to the player’s inventory when they receive the Bag at the very start of the game, this currently requires a fresh save file. It will not automatically appear on existing saves.

The Actual Proof of Concept

The goal was a reusable Rare Candy-style item: something you could keep in the Key Items pocket, use whenever needed, and never consume. Internally, I have been calling it Royal Candy, but the important part is not the name. The important part is that the proof of concept works.

On the surface, that probably sounds like a simple item edit. Rename an unused item, copy Rare Candy’s data, throw it into Key Items, and call it a day.

Sword/Shield does not make it that easy.

RomFS item data can create the shell of the item. It can give the item a name, description, pocket, shop entry, and basic “usable on Pokémon” behavior. But the actual Rare Candy behavior is not fully controlled there. The game’s executable decides what item routes into the Rare Candy flow, what gets consumed, what count the bag UI expects, and whether the item gives exact level-up behavior or fixed EXP.

That means this proof of concept required ExeFS patching.

To be clear: that is inherently risky. Editing ExeFS means modifying the game executable itself, not just replacing normal data files. A bad patch can break item use, crash the game, or corrupt behavior in ways that are much harder to diagnose than a normal RomFS mistake.

The interesting part is that this was made workable by building safeguards around the patching process instead of blindly writing bytes and hoping for the best. The patcher checks that the expected executable instructions are actually present before modifying them, only changes very specific known locations, preserves the original Rare Candy behavior, and writes the result as normal LayeredFS output. The goal is controlled patching, not random executable surgery.

Why Exp Candy XL Is Involved

One important detail is that this does not create a brand-new item ID out of thin air. The current proof of concept uses item ID 1128, which normally belongs to Exp Candy XL.

That item slot was useful because it already lives close to the level-up item pipeline, but it also created a problem: the game wanted to treat it like Exp Candy XL and give fixed EXP instead of acting like a true Rare Candy.

The patch works around that by keeping the useful route, but bypassing the fixed Exp Candy behavior. From there, Royal Candy can enter the real Rare Candy level-up flow instead of acting like a renamed Exp Candy.

Because Royal Candy takes over the Exp Candy XL slot, the install also replaces normal Exp Candy XL rewards with regular Rare Candies. That way, the player does not accidentally receive duplicate Royal Candies from pickups, shops, rewards, or other places where Exp Candy XL would normally appear. The reusable item stays unique, while the removed Exp Candy XL rewards still become useful level-up items.

How the Player Gets It

Royal Candy is currently granted when the player receives the Bag at the very start of the game.

That makes it feel like a natural part of a new playthrough instead of a debug item, shop workaround, or manual save edit. However, it also means the current proof of concept is built around fresh starts. If you install this on an existing save that already passed the Bag event, the item will not automatically be added.

So for now, the feature requires a new save file.

What the Proof Currently Does

Replaces the Exp Candy XL item slot with a custom Rare Candy-style item.
Adds that item without replacing the real Rare Candy.
Routes the custom item through the actual Rare Candy level-up flow.
Keeps the item in Key Items.
Prevents the item from being consumed.
Gives the bag UI a stable virtual count so it behaves properly.
Bypasses the fixed Exp Candy behavior that would normally get in the way.
Replaces normal Exp Candy XL sources with regular Rare Candies to avoid duplicate Royal Candies.
Grants Royal Candy during the early Bag event at the start of a new game.
Requires a fresh save file because existing saves have already passed that event.

Why This Matters

The bigger feature is that the item can be customized during install.

It can work as a purely infinite Rare Candy item, meaning the player can level freely without grinding. Or it can be configured to stop at custom level caps tied to story progress. Those caps can center around completion flags/work values triggered by major battles, such as important rivals, Gym Leaders, and other progression milestones.

That makes it useful for challenge hacks because it removes grinding without removing the intended level curve. Players can catch up new team members, rebuild after losses, or test teams more comfortably, while still being prevented from overleveling past the current progression point.

This is still a proof of concept, but it opens the door for a much cleaner quality-of-life system in Sword/Shield mods.