
Thamos ( ago) [on Bloodfang]
There are about 5 spots he can spawn: two wandering mobs on the southern wall, two static mobs inside the ruins (with one undead as a barrier between you and these inside mobs, not a placeholder), and the wandering mob between the tree and the ruins archway entrance.
You get about 2 pops per night per placeholder. If you want the second pop, the placeholder has to be dead before nighttime hour 0.