Rillaboom is a Grass-type Pokémon introduced in Generation VIII.
It evolves from Thwackey starting at level 35. It is the final form of Grookey.
Rillaboom has a Gigantamax form that was introduced in The Isle of Armor.
Rillaboom always carries its signature drum with it on its back, and pulls it out when engaged in battle. This bass drum is crafted from a tree stump, with several thick branch stumps protruding from it, which form both the legs of the bass drum as well as mid and high toms. Rillaboom also carries two drumsticks in its cuffs and takes them out to beat its drum.
By drumming, Rillaboom can tap into the power of its special tree stump. The roots of the stump follow the direction of drumming in battle. A Rillaboom with the best drumming technique can become the leader of its troop. Due to its kind disposition, it values harmony within the group. Rillaboom is very sensitive towards discord that could threaten the group's harmony, so it keeps a strict watch for such actions. Due to its strong sense of unity, it will ferociously defend its allies from trouble.
Rillaboom is the only known Pokémon capable of using the move Drum Beating and the exclusive G-Max Move G-Max Drum Solo.