Well werewolves are only out on a full moon (that’s a given). Now, if you kill a werewolf (via silver to the heart) it’ll turn back in to human form. Now, if you knock a werewolf unconscious and perform the mummification process (pulling out organs, wrapping, preserving, etc) you will have a mummy-werewolf. But how do you animate said mummy-werewolf? Simple: pace a curse upon the mummified werewolf. Then, when someone breaks said curse, voila, you have an animated mummy-werewolf. The only way to kill it is to find its heart in the jar and stab it with some sort of silver. Only an evil or crazy person would take the time to mummify it (perhaps a wizard or mad scientist). It also no longer needs the full moon because it was preserved in the werewolf state.