Utsuho, sun-devouring crow

flying
At the start of each player's upkeep or when
Utsuho deals combat damage to a player, put a radiation counter on each creature that player controls.
When a creature with a radiation counter on it
dies, it deals damage to it's controller equal to it's toughness + it's power.
On your upkeep, destroy all permanents with toughness equal to or less than the number of radiation counters on it.