Skeleton Key is a piece level 12 alien tech that as Kevin puts it is basically a "Get Out of Jail Free Card" that transport a person out of or into the Null Void Prison Dimension. 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.
In order to gain access to the final Sub Energy core located in the Null Void (inside The Wench/Grandpa Max's old hideout), Grandpa Max gives Ben a piece of level 12 alien tech called 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 emergancy and Vilgax succeeding in taking over the Earth definitely qualifies 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 it to power the Skeleton Key to teleport back to Ship where Grandpa Max, Gwen, & Kevin are waiting. Gwen & Kevin mention that Ben had only been gone a second (a fact which Grandpa Max found interesting). Afterwords Ben hands Grandpa Max a picture (taken during the summer the original Ben 10 series took place) he had left in the Null Void, looking at the picture Grandpa Max say "Best Summer of My Life". (referring to the summer in which the original series takes place).
- Kevin had heard of them but wasn't aware they existed until Ben 10 Alien Force: Vilgax Attacks.
- Is one of the few pieces of alien tech to first appear in a video game.