Or they may appear nowhere at all
I had game setups where a certain unit was just missing - like Ancient Ents and Archdemons (even if I beat Baal). The funniest thing was when I was playing the impossible paladin game - I scoured the entire elven lands and got no hunters whatsoever and when I beat a roaming party in demonis and opened up the sorcerer's tower - I found like 2000 of those
So as Elwin pointed out, Demonis is an option - but I wouldn't expect much, since by that point, you can have various other units to do the tanking for you - unless you decide to go on a low-level demonis raid (I remember raiding demonis around lvl 14), which is not applicable in your situation, since you're 27