Ashes of the Fallen

Found in a small packet, this coarse, foul-smelling black dust is made from the powdered remains of a celestial. Each packet of the substance contains enough ashes for one use. You can use an action to throw the dust in a 15-foot cone. Each spellcaster in the cone must succeed on a DC 15 Wisdom saving throw or become cursed for 1 hour or until the curse is ended with a remove curse spell or similar magic. Creatures that don't cast spells are unaffected. A cursed spellcaster must make a DC 15 Wisdom saving throw each time it casts a spell. On a success, the spell is cast normally. On a failure, the spellcaster casts a different, randomly chosen spell of the same level or lower from among the spellcaster's prepared or known spells. If the spellcaster has no suitable spells available, no spell is cast.