The Death Knight.
The Death Knight is an incredibly lame way to stop dead BD from leaving the game. Once evil kills you, you should stay dead. Evil can’t be resurrected as a death-immune killer ghost so why should BD?
A lot of games are turned by Death Knights when Evil played really well and should have been rewarded with the win. Sometimes you even have 2 Death Knights (4 guards and 2 CS) that have all the information from the last night of the dead people’s abilities, and possibly cooperating with a living Psychic and ALSO confirming living physicians in the process. And the Death Knights can communicate this information via deathnotes.
And the price of a Death Knight is simply a night without healing someone that probably didn’t need healing anyway.
Death Knight please go away, get out of this game.