Irthsa, the reaper's broker

at the beginning of your upkeep gain 4 health or
put a +1/+1 counter on Irthsa.
whenever an enemy player is reduced to 0 health
and does not have a bargain counter on them you
may have their life total become 8 instead of
them losing the game, then put a bargain counter
on them.
players with bargain counters on them cannot
attack you with creatures, or target you or
creatures you control with spells or activated
abilities.