Gamzee Makara is an Assist Trophy in Lawl Nova. When summoned, he'll sit down and ask the players if they want to buy potions. After that he'll throw colored potions at both sides of him. Getting hit by these potions will cover you with the liquid inside them, and will change your stats to the ones of the character represented by the color. Gamzee also has a different effect if he gets attacked. If this happens, Gamzee will get angry and smash the opponent with one of his clubs, dealing plenty of damage and knockback and making him leave the stage earlier.
Gamzee's potions (which are actually Troll Blood) are first introduced at the start of Act 6 Act 3, where he tries to sell them to Jane. Gamzee going berzerk when he gets hit is inspired by Gamzee's true nature when he's not under the effect of the pies (commonly refered to as Sober!Gamzee), where he is much more violent.