Violet is a giant mutant flesh-eating plant which was accidently created by Nigel Darkdoom. It appears near the end of book 1 when Ms Gonzales becomes trapped in one of her rooms in her giant, domed greenhouse. The Chief of security sends in some of his men to destroy her but they are killled and presumably eaten as Violet develops a taste for human blood.
Violet's vines break into the ventilation systema and wreaks havoc in the school by breaking into the rooms in a bid to find food in the form of H.I.V.E. students. Otto comes up with a plan to destroy her by overloading a group of sleepers over her head in the caves roof, thus crushing her. His plan is succesful and Violet is crushed and dies.