Tivra's Verminvow

You speak in a the tongue of the swarm, sending your forth your scourge to a point you can see within range. You create a 30-foot-radius Sphere of sickly yellow-green light. Any creature within this space must succeed a Constitution saving throw or suffer the Poisoned condition for the duration. Any creature who leaves or enters this space and has the Poisoned condition takes 1d12 Poison damage. A creature cannot take this damage more than once in a turn. For the duration, creatures other than you within this space have Disadvantage on saving throws to avoid or end the Poisoned condition.

Using a Higher-Level Spell Slot. The damage increases by 1d12 for each spell slot level above 1.