Unique Magic Item Cards found in the Greyhawk Wars boxed set was never fully capitalized on by others so now is the time! These items cannot be found in any form outside the "boardgame" rules until now. Enjoy the first set of three. I'll try to work on the last three next post.
Bowl of Storms
Wondrous item, rare
This item was originally created by the Sea Mages of Gradsul for use by the Keoland Navy. While this bowl is filled with water, you can use an action to speak the bowl's command word and cast the control weather spell. The bowl can't be used this way again until the next dawn. The bowl affords no protection to a user or his ship from the weather summoned.
The bowl is about 1 foot in diameter and half as deep. It weighs 3 pounds and holds about 3 gallons.
Rary's Bulls-Eye Bow
Weapon (long or shortbow), rare (requires attunement)
Rary first crafted this bow when he served as Archmage of Ket for use by the Beygraf's palace lookouts. When the first arrow is nocked on this bow, the next ranged attack roll you make against a target in that combat round has advantage on the roll. In addition, your target gains no benefit from cover, other than total cover, and you suffer no disadvantage due to long range. Subsequent attacks from this bow in the same round are made at the user's normal attack roll.
Bigby's Bottled Breath
Bigby was always experimenting with force spells, this potion was an early attempt of his to bottle one of his named spells that had unintended results. After drinking this potion, you can use a bonus action to exhale spectral force at a target within 30 feet of you. The target must make a DC 14 Strength saving throw, taking 4d6 force damage on a failed save, or half as much on a successful one. If the saving throw is failed the target is also pushed 5 feet away. The effect ends after you exhale the force three times or when 1 hour has passed.
Alternatively the user can try to break an object within range that isn't being worn or carried. The user makes a Strength check at +5 bonus.