Hi! That's a translation issue, sorry - I'll get it fixed for the next update!
It depends if you have fetishes that include Eldrich, demonic or mad science. Most likely the abandoned castle in my case because both demonic and eldrich are hard no. Deals with daemons never turn out well and if I'm not the largest monster in the end what is the point. If uncle Cthulu shows up I'm not the largest creature on the map any more. I think Malagar, eldrich and demonic cancel each other out. You can only have one of them and they are bound down to locations. Eldrich sunken temple. Daemonic abandoned mine. Malagar castle on the mountain.
-.- ... After you have chosen sunken temple or gold mine you get options to explore deeper parts in these bases. You can find your chosen allies in these deeper parts of your base. Cannot remember if you got option to explore these immediately after you have claimed these places or it toke some time like with Malagar before you get the option. I think eldrich wants priestess and Daemons want sky elf. I have not played with these factions so I don't know much about them.