An 8/8 for 21 with a minor (double edged) board clear seems like a skip-able mythic.
However, the Gisa and Gerralt/Necromatic Summons ability (if it includes discarded cards) seems like it it could be amazing with Liliana 1.0 or Ob Nix.
I’ve stolen him in event battles a few times and he just doesn’t seem to do anything, and with there currently being no black-blue or black-green planeswalker to be able to energize well enough to get that overload 2, I’m thinking that he’s probably passable.
Unfortunately, this is probably /thread until Aether Revolt. I thought that Live Fast and Deadlock Trap might be enough for Ob Nix to work with, but overload 2 would take a while.
Unless it is just completely OP, I’m gonna pass on any monocolor mythic they offer for sale. Just not enough bang for the buck, and this card doesn’t really impress me, although I would try it with G&G if I ever get it for free.