Whenever a creature you control
diesIs put into a graveyard from the battlefield. (CR 700.4), each opponent loses 1 life and you gain 1 life.
(You may
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.) // When you unlock this door, return all creature cards from your graveyard to the battlefield.
(You may
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)