This is a total conversion for Quake. Here an excerpt from the mod description:
The mod features 30+ richly detailed and uniquely themed environments to explore and a whole new army of monsters to test your skill and reflexes along the way. The beginning of the mod is full of portals in all directions that are visually themed by what lies beyond their black star veils. There is no fixed order or preferred path to how you explore this mod, the choice is yours.