So we ran into a situation where I had spawned some monsters already. The heroes revealed a new room and according to the booklet there were about 6 creatures in that room of which one was a master beastman. Having spawned earlier war parties, I did not have any master beastman figure in the box. I claimed that in this kind of situation I use replacement creatures and ASA I can use a real master beastman, I'll make the switch. My friend claimed otherwise, stating I could not spawn that creature there at all.
What's the official ruling?
To come to think of it, IMO I was right since let's say a big room is coming up with lots of...lava beetles as enemies. But since I had used many lava scout OL cards earlier, I can not spawn any monster in that area thus making it an empty room. Doesn't quite work that way, does it now?
Cheers,
Aamaxu