Some modded Egglocke saves boost the chance of hatching a shiny.

A cheery voice—familiar and yet huskier, like vinyl played on an old turntable—welcomed him. “Welcome to the Egglocke Challenge,” it sang. “Rules are simple: every egg you receive hatches into the partner that will walk this path with you. If a team member faints in battle, they’re gone forever. Collect three Gym Badges. Do not trade with outside cartridges.”

To play a , you typically don't download a separate "Egglocke ROM." Instead, you use a standard Pokémon Emerald ROM