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What Pokémon Emerald Rule-ette changes

How the game plays differently from Pokémon Emerald, then every stat, type and ability it alters next to what the official games do.

How the game plays

Emerald Rule-ette keeps Pokémon Emerald's story, map and Pokédex exactly as they are — Roxanne through Juan, Team Aqua and Team Magma, the Elite Four, Champion Steven — and builds a whole new challenge on top of it: the Battle Rule System. Every trainer fight rolls one or more of 26 possible rules at random, from a banned type or move category to a permanent Trick Room, an always-on Perish Count, or every one of your moves dropping to 1PP. Break the active rule and your Pokémon takes damage for it, so half the fight is figuring out what you're not allowed to do before it costs you. Two ready-made presets set the tone: Mystery Mode hides the rule and only docks half your Pokémon's HP per violation, while Mastery Mode shows you all three rules running at once and takes the whole HP bar for a mistake. Underneath the rules sit hard, badge-gated level caps enforced from the moment you leave Littleroot, and an option to swap every Gym Leader, Elite Four member and the Champion's team for a tougher, competitively built one. A built-in Nuzlocke mode adds permadeath, a dupe clause, a met-location clause and a bag lockout in battle, and a quick-access menu handles healing, PC access, move reminders and levelling without leaving the field. The game is built on pokeemerald-expansion, so the Pokémon data on these pages — stats, types, abilities and learnsets — is the engine's own current-generation values, not the original Emerald's 2004 originals; Rule-ette itself does not touch any of it.

The 26 Battle Rules

Which rule applies — or, with concurrent rules switched on, up to three — is rolled at random for every trainer battle. It is never a fixed fact about a trainer, so it isn't listed on any trainer's page, only here.

Breaking the active rule costs your Pokémon a chunk of its HP: half by default, or the whole bar on the harder preset. Some rules are held back from Gym Leaders, the Elite Four, the Champion and the other boss fights because the creator judged them too swingy for those.

Rule	What it forbids or changes
Banned Type	You may not use a Pokémon of one type, picked to always match something in your own team.
Banned Move Type	You may not use moves of one type, picked the same way.
No Healing	No healing items or healing moves.
No Crits	No critical hits.
No Recoil	No recoil damage.
No STAB	No moves that share a type with the Pokémon using them.
Only STAB	Only moves that share a type with the Pokémon using them.
No Super Effective	No super-effective hits.
1PP	Every one of your moves drops to 1 PP for the whole fight.
No Same Sex	You may not send out a Pokémon of the same gender as the opponent's.
No Switching	Any attempt to switch out is blocked.
Perish Count	Every Pokémon you send out gets a Perish Song counter.
Switch Moves	You may not use the same move twice in a row.
No Prio	No priority moves.
No Held Items	Held items may not activate.
No Ability	An ability's effect may not visibly trigger.
No Status Cond.	You may not inflict a status condition on the opponent.
No Setup	No stat-raising moves.
Trick Room	A permanent Trick Room for the whole battle.
No Physical Moves	No physical moves.
No Special Moves	No special moves.
No Status Moves	No status moves.
Inverse Battle	Every type match-up is flipped to its opposite for the whole fight.
First Move Slot	Only the move in your Pokémon's first slot may be used.
Truant	Every Pokémon you send out loafs around every other turn.
No Misses	You may not let a move miss.

From the game's own source code, v1.0.8.

The main changes

A Battle Rule System: every trainer battle rolls one or more of 26 possible rules at random — banned types and moves, no critical hits, a permanent Trick Room, an always-on Perish Count and more
Breaking the active rule costs your Pokémon HP, and which rule is active is never fixed to a trainer — it is different every time you fight them
Mystery Mode (a single hidden rule, half damage) and Mastery Mode (three known rules at once, full damage) as ready-made presets, or mix your own settings
Hard, badge-gated level caps in effect from before the first gym, the same numbers the creator's own level-cap sheet lists
An option to give every Gym Leader, Elite Four member and the Champion a tougher, competitively built team
Gym Leaders can be rematched at their own gym after the Elite Four, for a string of progressively harder teams
A built-in Nuzlocke mode: permadeath, a dupe clause, a met-location clause and no bag use in trainer battles
Keeps Emerald's own story, map and Pokédex — Brawly's badge is mandatory, and Champion Steven stands in for Wallace
Reusable TMs, a battle speed-up option, and a quick-access menu for healing, the PC, move reminders and levelling
Built on pokeemerald-expansion, so abilities, moves and Pokémon data reflect the engine's current generation, not Emerald's 2004 originals

How the Pokémon change

Measured from the guide's own data, so it can't drift from the pages it links to.

Compared against present-day official data. The Fairy type and hidden abilities arrived after Pokémon Emerald, so a difference here can belong to the series rather than to this hack.

Evolution methods for all 240 species →

Type changes (17)

Pokémon	Was	Now
Jigglypuff	Normal / Fairy	Normal
Wigglytuff	Normal / Fairy	Normal
Mr. Mime	Psychic / Fairy	Psychic
Togepi	Fairy	Normal
Togetic	Fairy / Flying	NormalFlying
Marill	Water / Fairy	Water
Azumarill	Water / Fairy	Water
Snubbull	Fairy	Normal
Granbull	Fairy	Normal
Ralts	Psychic / Fairy	Psychic
Kirlia	Psychic / Fairy	Psychic
Gardevoir	Psychic / Fairy	Psychic
Azurill	Normal / Fairy	Normal
Mawile	Steel / Fairy	Steel
Togekiss	Fairy / Flying	NormalFlying
Cottonee	Grass / Fairy	Grass
Whimsicott	Grass / Fairy	Grass