How to Change Your Pokémon's Type with Terastallization
Obtain a Tera Orb
You need a Tera Orb to perform Terastallization in battle. This is your primary tool for the gimmick and works similarly to other battle transformation items.
Collect Tera Shards
Gather Tera Shards corresponding to the type you want your Pokémon to become. Each type has its own shard variant. Give your Pokémon the appropriate Tera Shard as a held item before battle.
Use Terastallization
During battle, select the Terastallization option on your turn. Your Pokémon will transform, changing its type to match the Tera Shard it's holding. This affects move effectiveness and type matchups for the remainder of the battle.
Special Pokémon
Some species like Terapagos and Ogerpon have special Tera type handling built into the mod. Consult their individual pages for type-specific mechanics.
Obtaining Items
Use /genesis giveTeraShard <player> <tera-shard> to receive shards, or find them through gameplay.