Board Thread:General Grimm Discussion/@comment-283842-20150419001846/@comment-26322846-20150420191902

They're both spirits; I think that's the only significant similarity, as we don't know what other spirits (aside from Golem, which doesn't possess a human's body) there might be. The Hexenbiest spirit seems more akin towards a form of Necromancy, especially considering it requires the still beating heart of another Hexenbiest, and an elaborate ritual.

The Mishipeshu spirit seems more like an old remnant of an ancient deity, with a vindictive nature. I say this because as of yet, there appears to be only one, and it's speculated to have been worshiped as a deity, whereas there are many Hexenbiests.