Legendary Creature â Vampire
At the beginning of your end step, put a bounty counter on target creature an opponent controls. For as long as that creature has a bounty counter on it, it has "When this creature dies, each opponent draws a card and gains 2 life."
The target creature that gets a bounty counter still has the triggered ability it gains even if Mathas leaves the battlefield.
The opponents who each draw a card and gain 2 life are the opponents of the player who controlled the creature as it died. This may not be the player who controlled the creature when it received a bounty counter.
If Mathasâ€™s ability resolves two separate times targeting the same creature, that creature will have two instances of the triggered ability. Each triggers separately when that creature dies.
Creatures that receive a bounty counter other than from Mathasâ€™s ability resolving wonâ€™t gain the triggered ability. Creatures that receive more than one bounty counter as Mathasâ€™s ability resolves (most likely due to Doubling Season) wonâ€™t have the ability multiple times.