Circlet of the Sharpened Mind

Alter: This iron circlet has a magical pearl at its center and can hold up to 4 gemstones. When found, the circlet has 2 gemstones. A gemstone worth at least 5000gp can be added to the circlet over the course of 1 minute as it's magically drawn and fastened in place. While wearing the circlet, you can take a special Attack action on your turn to summon a number of floating, spectral swords equal to the number of gemstones in the circlet and make one melee spell attack with each of them against a target within 10 feet of you. You are proficient with these attacks and use Intelligence as your spellcasting ability for them. On a hit, the target takes force damage equal to 1d8+ Intelligence modifier. The swords appear at your side and remain there until; you dismiss them as a bonus action or until you fall unconscious or remove the circlet. While the swords are summoned, you can take this special Attack action once on each of your turns. The spectral swords shed bright light in a 10 foot radius and dim light for an additional 10 feet.

You can replace one of these melee spell attacks with a weapon attack as part of this special Attack action. If you're able to make multiple attacks when you take the Attack action, you can instead replace a number of these spell attacks up to the number of weapon attacks that you can normally take as part of the Attack action.

When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to make one melee spell attack with one of the summoned swords against the creature, rather than making an opportunity attack.

Attunement: Yes, Intelligence 17+
Rarity: Very Rare
Type: Circlet
Cost: 23850gp (with 2 5000gp gemstones)

Griffons Saddlebag, Vol II

Something about having 4 different gemstones in it?