Boom Bubble

A protective magical force surrounds you, manifesting as a bubble of warbling sound energy. You gain 5 temporary hit points for the duration. When you receive damage while you have these hit points, the remaining hit points are removed and the bubble explodes with a crack audible out to 300 ft, forcing all creatures within a 5-foot radius other than you to make a strength saving throw. Any creature that fails this saving throw takes 2d6 thunder damage, falls prone and is pushed 5 feet away from you, while a creature that succeeds takes half as much damage, is not pushed and does not fall prone. Objects within the radius also take 2d6 thunder damage.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the temporary hit points increase by 5 for each slot and the damage increases by 1d6 for each slot.