Aelita's Necklace

The Pendant is something that X.A.N.A. used to control Aelita in the episode Saint Valentine's Day. Aelita put it on, believing it was a gift from Jeremie. It implanted a special computer chip inside of the necklace, allowing it to bypass the material protection that Lyoko Warriors have from standard virus possession, and control her mind with an activated tower.