Trent's Spiritual Warding

You call upon Helm's favor, creating an aura of protective magic for you and your allies. For the duration, you cast a 20ft radius aura centered on yourself. The area is difficult terrain for creatures hostile to you. Additionally, whenever a hostile creature enters the area for the first time on a turn or starts its turn there, it must make a wisdom saving throw, taking 3d8 radiant damage on a fail or half as much on a success. Also, when you cast the spell and at the start of your turns after, allies within the aura gain temporary hit points equal to 3d8 plus your spellcasting ability modifier