Engulfing Slagwurm

Engulfing Slagwurm’s ability triggers and resolves during the declare blockers step. Creatures destroyed this way will not deal combat damage.

If Engulfing Slagwurm’s ability resolves and the other creature is not destroyed (perhaps because it has already left the battlefield or it regenerates), you’ll still gain life equal to that creature’s toughness.

As each ability resolves, the amount of life you gain is equal to the appropriate creature’s current toughness (if it’s somehow still on the battlefield), or its toughness as it last existed on the battlefield (in all other cases).