Nick Fury, the 62nd playable hero, and Medusa (team-up hero) are both on Test Center.
I've seen them both and I'm quite impressed with Medusa's skills and overall artwork.

Medusa's hair animations are a little outrageous at times, takes up a lot of space, but I think it's kind of funny and cool.
I know my Rogue will enjoy her stolen powers which is a toggle, physical damage & ranged attack from her hair.

I'm going to try and unlock Medusa for 600 eternity splinters. I think she'll be out soon (this week or next).
Nick Fury, I'll probably have to get him at a later time. I'm too busy cosmic prestiging multiple heroes.
And plus I had just gotten Black Bolt, Rogue, Beast, Thor and Storm recently which was 2000 ES.

My friend Wilfrid made the very first video discussing Medusa earlier this morning.