Pokemon Core Crystal ROM

Pokemon Core Crystal is a GBC ROM Hack by Sakaysen based on Pokemon Crystal in English. It was last updated on April 29, 2026.

Description

Pokemon Core Crystal is a Pokémon ROM hack, with the intended purpose of fixing Pokemon Crystal into a more polished, balanced, and overall engaging Crystal experience. I want to acknowledge and provide a huge shout-out to TheSmithPlays and the team that worked on Crystal Legacy. They made their code available on Git, which provided heavy inspiration and direct features that were implemented in my own game.

Fixes and/or adjustments in this rom hack will include the following: moves, learnsets for Pokémon, additional Pokémon, wild Pokémon locations, the Team Rocket storyline, the rival’s team & their storyline, teams on both normal trainers, Gym Leaders, Elite Four, and other bosses. In addition, it comes with many quality of life features that weren’t possible or weren’t considered when the games first came out.

Features

General

• Suicune’s base stats are slightly improved as a nod to the game’s namesake.
• Blue color palette priority to match the game theme (Male sprite is now also blue).
• Lugia and Ho-oh can be caught before fighting the Elite 4.
• Celebi Encounter is restored
• Ruins of Alph Fossil Pokémon added
• Legendary Birds have been added back
• Mewtwo and Mew encounters
• Pick your starting Pokémon options by region
• View Shiny Pokémon in the Pokedex
• TM Names now visible
• Exp. Share applies to all party Pokémon

Pokemon Changes

• GHOST type is now SPECIAL
• DARK type is now PHYSICAL
• FAIRY type added to the game.
• Trading is no longer required for evolution
• Evolution moves have been added
• The move menu for the party menu shows more information
• Stat Screen page for DV’s
• Happiness increases quicker and is displayed on the Pokémon stat page
• Base Stats reworked for certain pokemon
• Certain Pokemon Moves have had some rebalancing.
• Pokemon Route Encounters have been changed.
• Shiny ditto has been added as an option for the Odd Egg (1%).
• New Pokémon Additions – Togekiss, Honchkrow, Mismagius, Sylveon, and Weavile
• Pokemon Type Updates
• Typhlosion is now Fire/Ground
• Feraligatr is now Water/Dark
• Meganium is now Grass/Fairy
• More type changes are listed in the guide

Gym Leader, Rival, E4

• Gym Leader Parties reworked. Feature more Johto mons.
• Gym Leader Rematches added
• Rival Party has been improved
• Elite 4 Rematch Teams

Pokemon Battle Changes

• Gym Badge Stat Boosts removed
• Gym Badge Type boosts only apply to STAB attacks
• Removed the -30% chance for enemy Pokémon to land status moves
• Weather Icons in battle
• Time of Day Icons in battle
• Only Berry items can be stolen from the Players Pokémon via the move Thief
• Kurt’s pokeballs actually work as intended (Bugs fixed)
• HM Moves can be forgotten
• When a Pokémon levels up, its stat increases are displayed
• The move menu in battle shows additional information about the move.

Overworld Changes

• Viridian Forest has been added back
• HM moves no longer need to be taught to be used in the Overworld
• Evening has been added as a time of day
• Faster Nurse Joy Healing
• Item bag can hold more items (50)
• Berry bag addition
• Blackthorn Move Deleter also has a Move Relearner
• Berry bushes provide 1-3 berries
• Berry Bushes have berry sprites to show when they can be picked.
• You can fish while surfing
• Items in the overworld have updated sprites
• Pokemon in the overworld look correct rather than generic sprites
• Berry shop in Goldenrod
• Auto reuse repel prompt.
• I did not add running shoes since the only option I could easily find moves the player at the same speed as the bike.

Game Details

The following Pokémon have been removed from the game to make room for some additions: Lickitung, Shuckle, and Aipom. If those are some of your favorite Pokémon, I do apologize, but you will not find them in this ROM hack.

Changelog

V2.1.1

• Game would freeze when attempting to make balls from Kurt. Specifically when trying to select an amount.
• In “Extreme” mode the Secondary typing was not loading properly for the player’s battle mon. This resulted in the Player’s pokemon always have a secondary type of “Normal” in battle.

V2.1.0

• Addition of “Extreme” mode in the New Game options. Provides players with some fun thematic alternate typings.
• Addition of a “Shiny Ball” item. 100% catch rate that will force the caught pokemon to become shiny.
• A “Step Bar” option for the bike has been added. Allows players to continue to use the running shoes with the “B” button if they so choose.
• The Type Chart from Polished Crystal has been added as a key item. Available from the start in New Bark Town.
• The HM move “FLY” has been added to additional pokemon. Ex. (Gliscor).
• A dodge animation has been added for move misses.
• A flinch animation has been added.
• Quick Claw activation animation. Added for clarity.
• The DV’s for the Machop trade “Muscle” have been improved.
• Pressing “B” in the bug contest battle menu will now also place the cursor on “Run.”
• The sick Miltank Sprite will update from Blue to Pink when healed.
• Pressing “Select” in the battle menu will now display the enemy pokemon’s types.
• The “FLY” point in Cherrygrove was incorrect due to map changes. This has been corrected.
• Small changes to a couple pokemon’s learnsets.
• Enemy AI knows how to use Hidden Power properly, if its super-effective.
• Hail now increases defense for “ICE” type pokemon
• The move Toxic has increased accuracy when used by a “Poison” type pokemon.
• Battle text added for 4x effective and .25 effective moves.
• You can press “Select” in the Party menu to quickly move Pokemon

V2.0

• Updated the game to 60 FPS.
• Running shoes have been added as a middle speed between walking and biking. (Careful this is potentially missable!)
• Some optional battles have been added. (Agatha, Lorelei, Giovanni, and Professor Oak).
• New battle animations for Stat up and Stat down effects have been added.
• The pokedex now displays the Base Stat Total for each pokemon.
• A few bugs with the pokedex have been removed.
• Additional small tweaks to pokemon egg moves.
• Should be compatible with more emulators, simply due to reducing the game file size.

Useful Links

Pokecommunity

Documentation