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When you have 3 different creatures in a region (1 green spider, 1 blue Murloc, 1 blue Gnoll) Do you fight each creature with a separate challange action? Or would any damage left over after fighting a Blue Murloc and killing him, carry over to the Blue Gnoll on the next combat round?
You choose a monster group, however you have to choose a blue group as these are wandering monsters or whatever the rules' terms is. So you have to do a challenge action (as there are blue monsters) and you have to choose a blue monster group, and fight only that type of monster. So if nothing else changes, you will fit one bæue group thos turn, another blue next turn, and can then choose to attack the green in the third turn. Nothing carries over.