It sounds like this collaboration came on because BOC's Eric Bloom is a pretty avid Warhammer Online player. So he came in to tour the Mythic digs with fellow bandmate Richie Castellano, and recorded with Mythic's Brad Derrick and Josh Drescher. The song's lyrics, which are designed to tell people about the life of a Dwarf Slayer, were penned by Mythic Senior Creative Director (and recent Giant Bomb podcast guest), Paul Barnett. Here's what Paul had to say about it:
“We thought long and hard about how to properly tell gamers what the Dwarf Slayer is all about,” said Paul Barnett, Senior Creative Director for WAR and the song’s lyricist. “After going around in circles, we came to the obvious solution – we needed to write and record a hard rockin’ song, and we needed to do it with members of Blue Öyster Cult. If this song doesn’t get you fired up to shave your hair into a mohawk, dye it red, and play a Slayer, then you’re probably dead!”
The track is available for download on the official Warhammer Online site.