I have to agree with Ginyu that this is pretty weak. It costs too much for essentially a three card combo to kill a different creature. It requires the Angel itself to wait one turn, a creature that can be targeted that you would prefer to be dead, and CC that does more than 1 damage. That's automatically a duo already (for CC and possibly a creature like Voodoo Doll). It doesn't seem worth the investment.
Under the current meta its probably not that bad.
Honestly, this card is not weak at all. Its a 4|2 / 5|2 for 4
thats not exactly a wimp in terms of attack power, and a decent quanta efficient mid hitter would definitely benefit the element.
The ability does have some potential for auto-kill abuse. That would require either fractal or mitosis and some way to reliably kill off this creature at will.
Otyughs or Maxwell demons would do the trick, but both add in a third quanta requirement. I don't know if that would be worth the payoff or not... probably not for Maxwell demons at least... so an amusing form of otyugh chow might be the better option since otyughs are a little cheaper to pull off and get some added benefit in growing the otyugh.
If the bond has been used and the Angel gets lobotomized (or hit with AM / overdrive) will the bond skill still trigger when the Angel dies?
Also, what happens if the angel or the bonded target gets mutated?
(the mutation point is important since that could present a nice combo with fallen elf, this card, and mitosis)