Skeleton Keys are Level 12 alien tech that Kevin describes as a "Get Out of Jail Free Card" that can transport a person out of or into the Null Void. It appears as a plot device that allows Ben to enter and later exit the Null Void in the video game Ben 10 Alien Force: Vilgax Attacks.
Ben 10 Alien Force: Vilgax Attacks
In order to gain access to the final Sub Energy core located in the Null Void (inside Max's old hideout), Grandpa Max gives Ben a Skeleton Key, that he had obtained on the black market a while back. Kevin mentions he had heard of them but didn't know they were real until Grandpa Max showed it to them. Kevin explains it can be used to escape from the Null Void or as Grandpa Max states, it can transport a single person into the Null Void as well. Grandpa Max states he had kept it in case of an emergency. Grandpa Max also mentions he will need the Sub-Energy core to power it for the return trip back out of the Null Void.
Ben uses the key to transport himself into the Null Void and defeats D'Void, obtaining the last energy core, then uses the same to power the Skeleton Key to teleport back to Ship where Grandpa Max, Gwen, and Kevin are waiting. Gwen and Kevin mention that Ben had only been gone a second (a fact which Grandpa Max found interesting).
- Kevin had heard of Skeleton Keys but wasn't aware they existed until Ben 10 Alien Force: Vilgax Attacks.
- Skeleton Keys are one of the few pieces of alien tech to first appear in a video game.