Nakkorik, Ravenous Fiend

Menace
On each player's upkeep, they pay 1 life for each card in their hand. For each card that player has, they add {b} or {r} to their mana pool. They only use this mana to cast spells from their hand.
Each opponent loses 1 life and that player gains 1 life for each unused mana that player has on their end step.