17. Nor Iron Bars a Cage

Complete story — includes the ending

The mutated Kevin voluntarily imprisons himself in Incarcecon, a prison in the Null Void dimension, in the hopes of murdering the prison warden Morgg. In a flashback, it is revealed that Kevin was imprisoned at Incarcecon shortly after being sent to the Null Void in the original Ben 10 series, where he befriended a kindhearted prisoner named Kwarrel. Kwarrel helped Kevin escape from Incarcecon, but was killed by Morgg. In the present day, Morgg has converted the prisoner into a secret drug trafficking operation, forcing the prisoners to mine a hallucinogenic dust from beneath the prison. Ben and Gwen arrive at the prison to warn Morgg of the threat on his life, discovering the drug operation in the process. Kevin tries to kill Morgg but is thwarted by Ben, then flees. Morgg is arrested by the Plumbers, and Ben, believing Kevin is too far gone, tells Gwen he believes they need to "put him down."