We’re aware of the liking thralls have for lava and we’ve recently introduced some changes to how lava deals damage to help in that regard. We’re still looking at ways to make lava less appealing to thralls.
Our condolences to your thrall and its direct family.
I was helping a friend who got attacked by a purge in the volcano today. His base is placed on an “island” in the middle of a lava stream close to the entrance to the smelter place. He has bridges leading to the main land around it. We stood and watched in suprise as most of the purge waves, except the last one, all spawned in the middle of the lava stream and died. So it seems that not only followers do have a liking for the lava.