I have a party of 13th level characters, one of which happens to be a fighter who loves to swing her dual hammers at anything within reach. Recently I've been experimenting with some custom monsters and they are going to encounter a Gibbering Mouther/Minotaur hybrid, but before they get there I want to clear up a question I had.
Gibbering Mouthers have a trait called Gibbering, which reads as follows:
The mouther babbles incoherently while it can see any creature and isn't incapacitated. Each creature that starts its turn within 20 feet of the mouther and can hear the gibbering must succeed on a DC 15 Wisdom saving throw. On a failure, the creature can't take reactions until the start of its next turn and rolls a d8 to determine what it does its turn. On a 1 to 4, the creature does nothing. On a 5 or 6, the creature takes no action or bonus action and uses all its movement to move in a randomly determined direction. On a 7 or 8, the creature makes a melee attack against a randomly determined creature within its reach or does nothing if it can't make such an attack.
The part I was particularly interested in was the last part, where a creature who rolls a 7 or 8 makes a melee attack against a random creature within range.
Given that the fighter has 3-4 attacks normally, not including her Action Surge which can effectively double that, how many attacks should she be randomly making? Is she effectively using the full extent of her Attack action to swing wildly, or would she only make the 1 attack and call it quits?