Sheumi, the Fading Echo

Backlash (Whenever this creature is dealt damage, it
deals that much damage to that source's controller.)
Whenever Sheumi, the Fading Echo attacks,
untap a target creature. It gets +3/+3 until end of
turn, another target creature that dealt damage
this turn gets -5/-5 until end of turn. Choose a
target creature you control and target creature an
opponent controls. Each of those creatures deals
damage equal to its toughness to the other.