I like this card mechanic but the cost is WAY too high. It should get dropped a lot... maybe down to 4 quanta or less.
I don't think it's a 'counter to any creature' as you say. The only beneficial scenario you could use it now is if your opponent has few and strong creatures and you have many weak ones. And you even can't control which creature dies
It is a soft counter. Not to any particular creature, but rather to various status effects.
For instance, if the opponent relies on using adrenaline to buff small creatures, this could steal the adrenaline effect and give it to your creatures instead.
If they use plague to kill some of your creatures, this could end up spreading the plague to their creatures as well.
If they use momentum to bypass your shields, you can turn it against them.
So, while the selection is indeed random, you can still tip the odds in your favor by using a deck that has a large number of creatures.
I.e. if you have 10 creatures and they have only 2, then each status effect has a .2 chance of going to their side and a .8 chance of going to yours.
Employing this card alongside voodoo dolls further means that any negative effects get bounced onto the opponent as well.
For example, you have 9 skeletons and they have a crimson dragon. You pop it with mutation and it gives them a steam machine with the steal skill. You could then use this and you would have 90% chance to steal that steal skill and put it onto one of your skeletons, thereby keeping your own permanents safe and allowing you to steal from your opponent... I think that is a very beneficial use.
Its still a little underpowered, but I think I could see a few deck ideas that make it fun.
It certainly provides a very attractive means of dealing with SoW-PhaseShield decks.
(your example of mutation decks just means that you are giving your opponent random abilities as far as I see). Second question is, in said situation is the effect worth the 8/9 quanta investment?
You would use this by mutating the opponent's creatures then casting this (after making sure you have more creatures than they do).
The result is that if you accidentally give them a useful skill, you can try to steal it for yourself.
I don't think this spell is worth 8 / 9 quanta investment... at most it should be somewhere around 3 to 4
If this is made more specifice (i.e. only transfers positive buffs to your creatures and negative buffs to enemy creatures) then a higher cost could be justified (but 8 / 9 is still awfully high).