I'm playing a Bard in a 5E campaign. One of my most useful spells has been Dissonant Whispers. It's saved the party quite a few times but the question has come up and I've not found any answers in the rules as written for the spell. On a failed save, the creature takes 3D6 psychic damage and the spell causes it "to move as far as its speed allows away from you." However, there's no explanation as to how far it goes or if it ever comes back.
How far and for how long does the target run away?
(At present, we have have house ruled that it is gone for the duration of the battle, but we're considering a dice roll with a minimum of 5 rounds.)
Best Answer
It runs away from you at its normal speed and can return immediately
Dissonant Whispers (PHB p.235) states
So if the creature has its reaction available it uses its reaction to move its speed away. The creature does this immediately so it may not dash or do anything else to increase its speed or make the area safer or... anything. It just moves its speed away if safe to do so. Even if the creature had Dashed on its turn it doesn't matter since dash only lasts for the current turn.
The spell is instantaneous duration and doesn't list any lasting effects. While the DM could make a ruling like, "The creature is afraid of getting hurt again and chooses to avoid you", there is nothing in the spell forcing this to happen. The creature can choose to run right back toward you on its turn.