Is this a flying creature? ... if it is, sky dive would create some major issues...
Also, if one of them is hit by mutate or imporove, do they all get hit as well? And if so, how does that work out.
E.g. suppose one of them is hit by improve:
1) they could all get the exact same change (e.g. you get 4 copies of the same creature),
2) each gets hit by a seperate instance of improve.
This sort of thing is certainly very powerful. Its like dejavu plus.
Right now, we really have to work at it to pull off a good Fallen Druid deck. With this, its almost effortless.
-Quinted druid into play first.
-This + immolate then improve one tetrad => 4 improved mutants for 1 turn and 2 cards...
Immolate isn't even really necessary though, it just accelerates things to help avoid CC.
I can't say for sure if this is highly OP, but its certainly riding the line.
That said, the effect is very interesting. It reminds me alot of the "Trust" card that went through crucible a while back. If someone has the link to that card, it would be good to look through since many of the same issues will pertain here.