Gruell is the Triceraton slaver and a villain in TMNT series. He is voiced by Wayne Grayson.

When the TMNT were sent to the arenas, Gruell used them as target dummies for the competitors. The turtles defeated their opponents through teamwork and ninjutsu. Gruell tried to use his electric whip on Raphael but he was disarmed. The task master offered extra meal to anyone that can defeat the turtles. The TMNT gained respect from the gladiators after defeating them. Gruell and his guards got the slaves under control and prepared grum for them as a last meal before the battle. Gruell armed the gladiators with their weapons but made the TMNT fight without their weapons.