D&D 5E How to kill a devil that’s immune to fire. Flaming hot rock.

[ManBagel]

Erupting Earth
Choose a point you can see on the ground within range. A fountain of churned earth and stone erupts in a 20-foot cube centered on that point. Each creature in that area must make a Dexterity saving throw. A creature takes 3d12 bludgeoning damage on a failed save, or half as much damage on a successful one. Additionally, the ground in that area becomes difficult terrain until cleared. Each 5-foot-square portion of the area requires at least 1 minute to clear by hand.

A few questions. Is the damage magical, and what has resistance or immunity against this spell.

 

[jgsugden]

It is bludgeoning damage, so creatures immune or resistant to bludgeoning damage would be immune or resistant to the damage. The difficult terrain is just typical difficult terrain.

The damage is from a magical source, so I'd rule that it is magical bludgeoning damage, as one would get from a magic club.

 

[jaelis]

Many creatures are immune/resistant to bludgeoning damage from attacks. You'd have to decide if erupting earth counts as an attack for that purpose; I'd probably say no.

 

[Ovinomancer]

If the target has resistance/immunity to blidgroning fron non-magical sources, then this spell is fully effective. If it's just resistance/immunity to bludgeoning, full stop, this spell will be affected by that.