You attempt to capture and absorb a spell as it is cast by another creature, for release by you later. If the creature is casting a spell of 4th level or lower, its spell has no affect and is absorbed into yourself and held for later use, by you. If it is casting a spell of 5th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the creature's spell spell has no affect and is absorbed by you and held for later use, by you.

Absorbed spells can be held for up to one hour after which the magic dissipates without effect. Absorbed spells do not count against your total number of spell slots or spells available and can be cast using an action. 

You may store a number of spells equal to half your spell attack modifier. If this spell is cast when you have no more room for absorbed spells, the spell is countered but not absorbed. You may use an action to get rid a stored spell, instead of casting it, the magic being diffused without effect.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the spell is absorbed without effect if its level is less than or equal to the level of the spell slot you used.