I apparently got a little confused in set up. When you choose your monster groups, you set them up according to the Group Limit for the number of players, correct? For example, the Ettin in a 3 player group would be just one Master Ettin, or did I get that wrong?
And when gaining reinforcements at the end of the OL's turn, can one of those monsters be a Master as long as it abides the Group Limit?