The confusion effect on the Gibbering Mouther and Umber Hulk contains this text:
On a 1 or 8, the creature makes one melee attack against a random creature, or it does nothing if no creature is within reach.
Does this infer that it is allowed to move to any creature within its range of speed? Or it just has to stand still and attack an adjacent creature if able?
Reach is term defined in the rules - it is the area around a creature with which it can attack someone with a melee attack. It is normally 5 feet but some creatures' attacks and some weapons have a greater (or lesser) reach.
With that in mind the sentence is easy to parse - if there are creature(s) within its reach it attacks one of them (once) at random, if not it does nothing - in neither case will/can it move.
