Circle of Protection

A circle of blue rippling energy of arcane words expands out of you for 15 ft. Any hostile monster (to you) cannot enter the circle. Instead, they attack the circle. The circle has 20 hit points, with an armor class of 15. Once the circle's hit points reach 0, the circle dissipates and all hostile monsters can enter within the circle

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the hit points of the circle increases by 5, and the armor class of the circle increases by 1 for each slot level above 6th.