Xir Crystal

See Dwarven Artificers, specificly Artillerists for more information on this topic.

Dwarven Artillerists are another group that came about due to the evolution of siege engineering. Unfortunately, they don't have access to the more stable forms of gunpowder that those on the surface have. As such, they have to utilize the more unstable Xir crystals which are ground down, and placed in a pool of water along with other ingredients. It then ‘ferments’ for a week before becoming a thick muddy brown paste that explodes violently when exposed to fire. Though there are many uses for this block putty as it's called, it must be kept within a metal container lest it get too hot and explode. Due to how easily it explodes, only the truly mad sign up to wield a blast stick and slay their foes with fire and fury.