The Warpstone is magical tower in Vermintide. Its known as Wyrdstone as well.
Summary
The very stuff of chaos, it is theorized that shards of the emerald mineral fall from the Chaos moon Morrslieb. Considered by many if not most to be a burden more than a boon, with proximity causing madness, mutations and death. The Skaven however are enamored with the substance and utilize it in many ways in their society.
Ranging from tokens to currency, power sources for their technological creations or even ingested by some to increase their strength and ferocity; the Skaven value Warpstone above all else. Some even think the Skaven may have been mad enough to attempt to pull Morrisleb closer to the world in an effort to collect more of the substance, if not pull the entire celestial body to the ground itself!