Sword of the Spelldrinker

Weapon (longsword), legendary (requires attunement)

This sword seems to absorb any light that touches it, making it appear darker than the deepest midnight. You gain a +3 bonus to attack and damage rolls made with this magic weapon, which deals an additional 2d8 radiant damage on a hit. While you hold this sword, you treat any magical light, darkness, or atmospheric effect within 30 feet of you as if it were nonmagical and breathable.

In addition, this sword has 3 charges and regains all expended charges over a long rest. While holding the sword, you can expend 1 of its charges to cast the counterspell spell at 5th level from it. If you successfully interrupt a spell in this way, you can choose to absorb it into the sword instead of countering it. The absorbed spell must have a casting time of one action or bonus action. The sword can have only one absorbed spell at a time.

You can use an action while holding the sword to release an absorbed spell. When you do, the spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster, but is otherwise treated as if you cast the spell.

The interrupted spell remains absorbed by the sword for up to 8 hours or until released. Absorbing a new spell replaces the one stored within the sword.

The sword glinted in the light of the fire. No, not glint. It… drank the light in, it seemed.

She pried her attention away from the beautiful blade long enough to utter a single word. In an instant, the fireball hurtling towards her was pulled deep into the sword's inky depths. The sound of the archmage's frustration forced a small smirk to tug at the corner of her mouth.