Thank goodness you posted when you did because I just remembered something really important and would've double posted it otherwise.

SO URTELEM RIGHT. They spend a lot of time curled up sleeping and have a relatively slow metabolism, and their diet is relatively low in nutrition. That doesn't matter too much, because they have magical effects on stone and sand and such, which could help out a lot in moving their muscles and keeping them warm.

Having a body made of rock is kind of weird thermally speaking. It'd take quite a long while to heat up or cool, and because it's hard to liquefy, there's not exactly a 'blood flow' to equalize temperature (I assume they do have blood, though, either in highly mineralised water or a stone paste or both). They're also big boys that probably retain heat quite well due to sheer mass, much like whales and moose and such. So there's an argument that their body heat is relatively stable.

However, their activity can also vary tremendously, and I assume magic requires resources of its own. When resting in bouldermode, urts probably cool down, and then get warmer when they're doing high-energy stuff like punching whiny bitches. Depending on region, they also spend a lot of time taking in sunlight as an additional heat source. Because of the slow heating of rock, there's also most likely a considerable temperature gradient in their body in daytime. So they might also have a rather high temperature tolerance range. Anyway.

The point is that urtelem probably want to stay warm every now and again, without expending too much magic, and while sitting pretty still.

They're also rather artistic, and, increasingly, traders.

Guys. Urtelem wear clothes. They totally wear clothes. 

Sometimes. Kind of. A little. Probably mostly decorative blankets. And mostly at night. But still. Clothes, guys. Clothes.

ed: dude. guys. you could totally meditate on a herd of urtelem at night. just pick one of those big friendly-looking boulders and. sit on it. on a blanket. they wouldn't mind. it would be awesome. wow.

ed ed: friendly reminder how urtelem also build howdahs on themselves to carry goods and passengers, but. like. it doesn't stop there. you could build anything. build a shrine. build a cannon. build a pigeon coop. build a fucking windmill. do it. just have urtelem walking around with these increasingly lofty constructions on them and not giving a single fuck because they have the structural integrity of literal bedrock. just use balsa wood or something. they are their own mobile settlements. this is canon. this is so canon.

I just achieved rock person nirvana, guys.