Condense

When you see a foe cast a spell that has an AOE of any size you can use your reaction to condense down the size of the area to a 1-foot wide sphere, make a DC17 constitution saving throw, on a success you successfully condense it and the next creature to enter the area takes double the damage of the original spell. On a failed save, you fail to contain the spell and its area increases an extra 50% and deals damage as usual. This condensed spell disappears at the end of your next turn.