Rapid growth. When created by the Zehir root ritual, these vines grow to envelop any building or structure targeted by the caster of the ritual. The growth is fast enough to cover an entire tower in a night but will take more time to encompass larger structures. Rapid growth is only possible if the plant is placed on top of open soil, and sprouted in the living body of a humanoid. 

Entangle. Any creatures encountering growing vines must make a DC 12 Str save or take 8 (2d8) force dmg and be grappled. Every subsequent turn the vine continues to crush the target (2d8 force dmg) until it is dead or free from the grapple.

Poison cloud. When vines are reduced to 0 hit points, they explode in a poisonous gas cloud.  Everyone in a 5ft radius must make a DC 12 Con saving throw or take 7(1d12) poison damage or half as much on a save.

Life drain. Any creature reduced to 0 hitpoints while being within 5ft of a vine, is engulfed by the growing vines in 1 round. The vines keep the creature barely alive as long as they stay alive themselves.