A mimic's disguise fools its victims just long enough to draw them within range of its venomous tentacles.

Eventide

Woodlurker Mimic

Whenever you play a spell that's both black and green, Woodlurker Mimic becomes 4/5 and gains wither until end of turn. (It deals damage to creatures in the form of -1/-1 counters.)

Whenever you cast a spell that's both black and green, Woodlurker Mimic has base power and toughness 4/5 until end of turn and gains wither until end of turn. (It deals damage to creatures in the form of -1/-1 counters.)