Phantump is a ghostly Pokémon possessing a tree stump. Its black body is wispy with nubby arms. Covering its head is a small, brown tree stump with a wavy branch on each side. Its red eyes are visible through two holes in the stump and its mouth appears on the stump itself. There are two small, green leaves near the tip of each branch. Brewing these leaves can create a curative liquid.

Phantump is created when a spirit possesses a tree stump; it is said that the spirit is that of a child who became lost in the forest and died. This Pokémon's cries sound like the voice of a child or eerie screams. People have become lost following the voice, but Phantump is attempting to make friends. Phantump along with its evolution Trevenant are the only known Pokémon capable of learning Forest's Curse.