Ben 10: Ultimate Alien

Ben 10: Ultimate Alien is the third series in of the Ben 10 franchise; it is the sequel of Ben 10: Alien Force. In the series  Ben and Gwen are now 16 and Kevin is now 17; they continue to fight aliens. Ben's Omintrix has been destroy but he has a new device, the Ultimatrix, that allows him to evolve his aliens into their ultimate forms.

Episode 27: The Creature from Beyond
The Forever Knights think they have a cache of weapons; when they open the door they release a creature called a lucubra. The creature feeds on the part of the mind used during prayer and meditation. The lucubra attacks and feeds upon a policeman and through him he feeds upon Gwen. When Kevin frees both, the lucubra takes squire Winston and runs off with him. When Kevin, Ben, and Gwen find the creature, it is feeding on the policeman, Winston and two Forever Knights who are released by the creature to attack Ben and Kevin. Gwen, having been fed upon, is under its influence until Kevin covers her head with an iron plate that breaks the influence. Ben uses En-er-gy to make a hole and Gwen reproduced the cover to banish the lucubra and break the influence. In the end, Winston is shown to still be under the influence of the lucubra as his eyes glow green.

Episode 42: A Knight to Remember
After the Lucubra incident, now Diagon can possess Gwen.

Episode 43: Solitary Alignment
Azmuth reveals his past with Sir George; in earlier times the lucubra invaded earth and George was the last knight standing. We see a lucubra feeding on a knight and that knight fighting other knights.

Episode 51 The Ultimate Enemy part 1
Diagon possess Gwen once again to make Gwen free him from the seal.