Khelben's Dweomerdoom
9th-level abjuration (Sorcerer,Warlock,Wizard)
- Casting Time: 1 bonus action
- Range: 30 feet
- Components: V, S, M (A crystal lens worth at least 1,500 gp, which is consumed in the casting)
- Duration: 10 minutes
You counter an opponent's spell before it is even cast, without knowing what spell you are countering. When you cast this spell, the target loses the ability to cast the highest-level spell it knows (or has prepared, if it prepares spells) for the duration. If the creature knows (or has prepared) multiple spells of that level, the DM randomly determines one of those spells. Until the spell ends, the target cannot cast that spell by any means.
In addition, if the target uses spell slots to cast spells, it loses one spell slot instantly when you cast this spell. The lost spell slot is of the highest level for which the creature currently has slots. After this spell ends, the spell slot is regained. If the target has 9th-level spell slots, or the spell it would lose the ability to cast is 9th-level, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, this spell works normally. On a failure, the target can make an Intelligence saving throw to negate the effects of this spell entirely.
This spell has no effect on creatures that cannot cast spells.