Undergrowth — Target creature gets -X/-X until end of turn, where X is the number of creature cards in your graveyard. If that creature would die this turn, exile it instead.
原文The value of X is determined only as the undergrowth ability resolves. If the number of creature cards in your graveyard changes later in the turn, the target creature is unaffected.
原文Necrotic Wound's replacement effect will exile the target creature if it would die this turn for any reason, not just immediately after Necrotic Wound resolves.