Arena of Light

You create a massive arena of light centered on you with a radius of 50 ft.  All allies within the arena have their next attack made with advantage and deal an additional 3d4 radiant damage.  If the arena is still up at the start of your next turn, you can collapse it and all enemies inside must make a Wisdom Saving Throw.  If they fail, they take 3d8 (+ Wisdom Modifier) radiant damage.  

If cast at the 4th level, the radius of the arena is increased to 75 ft, all allies' attacks deal an additional 3d4 radiant damage (but only the first is made with advantage).  When and if you collapse the arena, it deals 4d10 (+ Wisdom Modifier) radiant damage to all enemies who fail the Wisdom Saving Throw.