|Role||Guardian of the Boulder Magisword, Cave Weirdo|
|Friends||Prohyas, Vambre, Skullivan, Lady Hiss|
|Voiced by||Kyle A. Carrozza|
Prug is a dragon and the brother of Grup. He is very similar to Grup in terms of appearance, voice and personality, but is significantly larger. He formerly served as the Guardian of the Boulder Magisword until it was retrieved by Prohyas and Vambre and now works at the Cave of Stuff as a cave dragon alongside his brother.
He first appeared in "To Boulderly Go" inside a cave, where Vambre and Prohyas approach him for the Boulder Magisword. They ask him if they can have the sword, in which he willingly agreed. After Prohyas used the sword, it generated a boulder that sealed the cave, trapping them all inside. Prug suggested to play hide and seek despite the fact that it's impossible to do so in the cave. Its revealed in "Random Acts of Memory" that Nohyas freed the three from the cave, right before Nohyas made them forget Prug existed.
He appears in the short "Working Grup", alongside Grup and his Cave Weirdo friends in the Cave of Stuff. Grup introduces him to Prohyas and Vambre and he acknowledges that he had been trapped in a cave with the two before, but Prohyas and Vambre have no recollection of the event.
Prug makes his first re-appearance since the series' first short in "Cleanliness Is Next to Grupliness" commenting on Skulliver's jar-ham nose.
In the episode "Biggest Fan", he and Grup served as sharks in the Cave of Stuff for Glori to get the Warriors to save her. He later brings Glori to the Warriors since they want her to leave due to her being a terrible actress.
He and the other Cave Weirdos made a slight cameo in "Little Sword of Horrors" where they tee pee Prohyas watering his Carniverous Plant Magiseed.