Vairis Sil, Dungeon Master

Whenever a creature dies, roll a d20. If the
number rolled is greater than or equal to the
creature's converted mana cost, return that
creature to the battlefield under your control.
{u}{b}{r}, Roll a d20: Target creature you control
but don't own gets +X/+0 until end of turn,
where X is the result of the d20.