Confining Flames

You create a swirling vortex of flame that fills a circular area with a radius of 10 ft centered on a creature you choose within range.  Any creature entering the area for the first time takes 2d6 fire damage and takes another 1d6 for each turn it starts in the flames.  In order to leave the affected area the creature must succeed on either a Dexterity (Acrobatics) or Strength (Athletics) check with a DC equal to the spell save DC of the caster.  On a failed save the target is pushed back by the flames and is forced to remain in the area until its next turn.

At Higher Levels.  When you cast this spell using a spell slot of 3rd level or higher, the damage taken from entering the area increases by 1d6 for every slot level above 2nd.