When you take a single source of damage, you create a protective ward that has 18 hit points. The ward absorbs up to its total number of hit points from the attack.

Once the ward absorbed damage in this way, it goes inert until you release it the next time you deal damage. The number of hit points absorbed by the ward is added as force damage to your next attack, spell, or similar.

At Higher Level. When you cast this spell using a slot of 4th or higher, the ward gains 6 hit points for each slot above 3rd.