[RPG] Is the Moonbeam spell amazing, or are we doing it wrong


The description of the moonbeam spell (PHB pg. 261) says:

When a creature enters the spell's area for the first time on a turn or starts its turn there, it is engulfed in ghostly flames that cause searing pain…

On each of your turns after you cast this spell, you can use an action to move the beam 60 feet in any direction.

We read this to mean a creature takes damage from moonbeam when any of the following conditions are met:

  • It begins its turn inside the moonbeam
  • It enters the moonbeam on its turn
  • The creature finds itself inside the beam on another character's turn, no matter how it got there

The creature will not take damage in the following instances:

  • A creature moves from one part of the beam to another (obviously it had to take damage, but it won't take more damage)
  • A creature is in the beam after having been inside the beam already on that turn.

Following these assumptions, our druid cast a moonbeam and did damage to two enemies, Bob and Frank. On their turn, they took damage again, killing Bob. Frank left the beam. On the druid's next turn, she moved the beam in a circular motion, not exceeding 60 total feet of movement, and in the process the beam came in contact with a dozen enemies and ended on Frank. All dozen enemies received damage, as they were inside the beam at some point during the turn. On Frank's next turn, he again took damage for the fourth time and died. On each of the druid's turns, she moved the moonbeam around like this until the fight ended (it did not exceed the time limit and she made all concentration checks).

Is this a legitimate use of moonbeam? It seems awfully powerful for a level 2 spell.

Best Answer

In a tweet from Jeremy Crawford, he says:

When a spell's description uses "enter" in relation to an AoE, the entering has to be voluntary only if the text says so.

By itself, it seems to imply that moving the Moonbeam counts as "entering".

But, in a Sage Advice article, he clarifies this:

Our design intent for such spells is this: a creature enters the area of effect when the creature passes into it. Creating the area of effect on the creature or moving it onto the creature doesn't count. If the creature is still in the area at the start of its turn, it is subjected to the area’s effect.

Entering such an area of effect needn't be voluntary, unless a spell says otherwise. You can, therefore, hurl a creature into the area with a spell like thunderwave. [...] Keep in mind, however, that a creature is subjected to such an area of effect only the first time it enters the area on a turn. You can't move a creature in and out of it to damage it over and over again on the same turn.

In summary, a spell like moonbeam affects a creature when the creature passes into the spell’s area of effect and when the creature starts its turn there. You’re essentially creating a hazard on the battlefield.