Marten, Master of the Doomed

Whenever Marten deals damage, target opponent
loses that much life, whenever Marten takes
damage, you lose that much life.
Pay 5 life, {b}{b}{b}: you may return a creature from
your graveyard to the battlefield, any opponent
may pay 5 life, if they do, counter this ability.
Whenever Marten leaves the battlefield,
return it to the battlefield transformed.