Originally posted by Rhapsody:

The totem pole things are separate, I think.

I guess there's a decent chance that the boss altars are constructed of many pieces with textures being drawn over them to distinguish Moder and Yagluth altars. Elder's altar structure probably consists of many objects as well. But it seems weird that altar of Biomass or nothing related cannot be found on the list... or at least I can't find anything like that.

Yeah, I couldn't either. I presumed they were unique structures because they cannot be destroyed. I know it's possible to spawn some structures that cannot be destroyed (like statues), but I can't seem to figure out how to spawn things like boss alters or drake nests.