The remaining are in PC settlements (you have to travel though pc areas to get to them). Thats only 3 I think though, not 9.
Thanks. People say there are 27 altars, but I only found 18 in the area below the PC (although the altar at the Auction cost my character 17 years of life, and then the altar at the trading post—with a super-crit—cost another 18).
