I'm not planning on using him anywhere.  He looks good in clan boss and fairly meh everywhere else.  If I was a brand new player though it would be different.  Even the bad leggos would be decent epics and you'd take a decent epic any day of the week.  Depending on what I end up doing with my clan boss team (my next project), I might use him but he is way down the list of legendaries that I already have or am about to get when it comes to books and I don't have many legendaries.  Scyl, Arbiter, Rhazin (if I get the last champ... as I've been saying for months now), Ursaga, and Riho would all be ahead of him.  Versulf might be ahead of him depending on how good he looks in the doom tower.  I might change my mind depending on how good he'd be for my clan boss team but Scyl/Arbiter/Rhazin would still be ahead of him.

I havent seen his multipliers, but might build him as a slow nuker for arena with good accuracy if the damage on his a3 is good. My current nuker is force, so i could sub him in when facing spirit.

The odds are that the damage will be moderate however given it has a freeze effect as well, i could use him in single turn meter teams (turn meter, drop defence, nuke, then freeze) but it just depends on the numbers.

faction wars for shadowkin when it shows up. thats about it I guess

mine will be guarding my vault for the forseeable future.  i have a bunch of legendary champs i've already leveled and ascended that i can't book already.  don't really need another in the rotation