Large Object

Armor Class: 15 
Hit Points: 30

Toxic Keg (Requires Load and Aim). Constitution Saving Throw: DC 15, each creature in a 20-foot-radius Sphere centered on a point 30 to 300 feet from the launcher. Failure: 14 (4d6) Poison damage. Success: Half damage.

A back-mounted, wooden catapult flings small kegs of toxic gas. Loading a Keg Launcher requires the Utilize action, and aiming it requires another Utilize action. Then a crew member can take the Toxic Keg action.