Garnet, Clairvoyant

Gem Fusion (When this enters the battlefield,
exile two other Gems you control and put a +1/+1
counter on this for each color it shares with those Gems.
Otherwise, sacrifice this. When this leaves the
battlefield, return those Gems to the battlefield under
their owners' control.)
Whenever a player casts an instant spell, choose
one: Scry 1 or target Gem you control gains
+2/+0 until end of turn.