Moulder is a zombified version of the Pokémon Grimer . It is one of many zombies that appears in the ROM hack, but it is one of only two species that are obtainable in the wild, the other being Graveill. It evolves into Yuck at Level 38.
Pokedex Entry:
Type: Dark Sludge Pokemon
HT / WT 2'11" / 66.1 lbs.
Once a GRIMER, now a risen corpse that was arguably never even alive, MOULDER is a festering pile of foetid flesh and pus. Beware its toxic tongue.