Noxious

The Noxious Strain is a variant strain of the ultralisk that appears in Heart of the Swarm.

Overview
During Kerrigan's resurgence, Abathur discovered the Noxious Strain in a Dominion xeno research facility on Korhal. The Dominion scientists inadvertently created a potent toxin which was deadly to any non-zerg entity. The toxin was used to kill a few ultralisk that managed to escape captivity in the facility. However the ultralisk managed to bond with the toxin thus forming the Noxious Strain. The Noxious Strain is able to release toxin vapors in a controlled manner through the vents in its carapace.

Game Unit
The Noxious Strain is able to emit Noxious Clouds that deals 5 damage per second to nearby enemy ground units. Its Toxic Blast ability deals 20 damage to enemy ground units and structures. Toxic Blast has a 10 second cooldown.