Warpstone was an independent magazine that covered the topic of Warhammer Fantasy Roleplay.
Warhammer materials described warpstone as solidified dark magic with transmutatory and alchemical powers.
From April 1999 until their closure at the end of 2002, Hogshead Publishing assumed control over distribution of Warpstone, which made it possible for them to publish material that they were unable to use in official Warhammer publications.
This happened to coincide with a Cease & Desist letter from GW, which delayed further publication while this was resolved.
The final issue 30 was eventually released in November 2014, as a bumper farewell edition.