[Edi]

I'll try to answer your questions as clearly as possible.

General movement rules:
- Standard units have 3 Action Points, Slow units have 2 and Fast units have 4
- Terrain costs 1 or more AP to move through (plains 1, forests 2 etc)
- If moves cost more AP than you have left, the rest is deducted from your AP next turn
- Immobile units can't move (duh!)
- Various movement related special abilities reduce some terrain AP costs

General rules about terrain guards:
- Monsters that guard special terrain do not move
- Animal guards are more liable to wander, and usually only from Ancient Forests
- Monsters spawned in random terrain squares (not special terrain like mines or ancient temples) wander around


In this specific case, based on these rules, we can deduce the following:
- The Haunted Capitol is a special site, therefore its guards don't move (the things it spawns, on the other hand...)
- The Horror Olm is a slow unit (snail icon, last in list), therefore has 2 AP if it were to move.
- The Slave to Unreason is an immobile unit (last icon in list), therefore it does not move no matter what.


So in this case there is no fear that either of those is going to charge out of the capitol gates anytime soon. Poor Barras just doesn't know that, but he knows enough to suspect and is suspicious enough to expect that something else might come out of there.

Of course, there are things like Manticores, Chimaeras, Catoblepas and Dracolions that can appear as random wandering monsters. Starting next to one of those and getting caught unawares can mean instant game over. I remember one test necromancer who got a manticore right next to the Dark Citadel and it attacked on turn one. Got left with one or two crossbowmen out of his entire starting army plus animated undead and that only through a fluke of luck (one crossbow landed a 29 point hit, which allowed victory, just barely).

As far as the next installment, I'll see whether this evening or tomorrow sometime.