Wondrous Item - Very Rare (requires attunement by a spellcaster)
This band of intricate silver and gold is set with three gemstones - a ruby, a sapphire, and an emerald. Dwarf runes are etched into the inner surface of the circlet, and a gentle glow emanates from within the stones when a spell is concentrated upon. The circlet allows its wearer to harness their mental prowess in unprecedented ways, but at a cost.
While wearing this circlet, you can choose to concentrate on two spells at once. When you do so, the circlet's gemstones hum with energy, and you can maintain both spells for one round. Once this effect has been activated, it cannot be used again until the next dawn.
If you wish to extend this period into a second round, you must succeed on a DC 15 Constitution saving throw. If you fail the saving throw or choose not to extend the duration, the first spell you were concentrating on ends immediately.
Each time the effect of the circlet is used, the DM rolls a d20. On a roll of 1, the gemstones shatter, causing the item to lose its magical properties. The energy backlash also forces the wearer to make a DC 15 Constitution saving throw. On a failed save, they take 2d8 psychic damage and are stunned until the end of their next turn. On a successful save they take half the damage, and is not stunned.
The dwarven rune inscription reads: "In unity, there is strength; in ambition, a downfall."