The bigger they are...
The enemies just got bigger as I went deeper into the altar complex. Giant knights, giant(er?) hounds, even this giant stone atronarch. Their size didn't matter though, as the same shadow technique served me well.
There was even a familiar looking, reptile type critter: a daedroth! Ironically it was probably the weakest thing in this place, requiring only one combo to eliminate. It must help that I can close the distance so fast that it still counts as a sneak attack even if I come from directly front.
These giant goatmen did scare the heck out of me though. They were strong, resilient and most importantly - bloody fast. They could outrun me even with my darkness speed boost.
Might be related to Baphomet?
Every time I encountered them it required a decent amount of potion drinking: health, invisibility, stamina. The slow time shout also helped.