Spike and Xander are sent to an alternate dimension where they find themselves in a desert-like landscape; Spike hunts the deer(-like creatures) that flit across the land, and they find shelter in a cave? Xander is attacked by a native creature sort of like a monkey shortly after they arrive in this place. They're there for some time, long enough for an encounter with an uber-nasty that is attacking them in the cave just as a portal is opened up to bring them back.
Am I imagining this or is it an actual fic somewhere? lol, help is very much appreciated! :-D