There are two artists with this name:

1) Fierce Deity is the project of Thomas Dorton from Delaware. It's largely inspired by free jazz, drone and krautrock, with some influence from black metal, post-rock, prog, shoegaze, psychedelia, minimalism, and '80s punk & alternative.
2) Fierce Deity is an Australian neo-retro metal band, started by Jonathon Barwick formerly of Taberah, whose lyrical themes revolve around video games. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.