This mod adds artillery shells filled with mustard gas. It was highly inspired by Optera's Poison Artillery Shells mod.
The mustard gas shells do less damage that a regular artillery shell, but create a deadly mustard gas cloud on explosion. The cloud stays for a while and moves with the wind, so be careful where you shoot. The mustard gas only damages living entities (biters, worms and the player), while the shell explosion itself also damages buildings.