Item
Thunderstone
The shortest noise can interrupt the longest spell
Primary ingredient: A thunderstone nodule, a hollow mineral from Askenon that stores vibrations.
This mineral shell erupts in a sharp detonation when it strikes the ground. Throwing it is a general action of 1 tick. It affects a 10 ft radius around a point within 30 ft. Every creature able to hear makes a Fortitude save against DC 18.
On a failure, a creature is deafened and can neither speak nor use a verbal component until the end of its next turn. Any verbal spellcasting in progress is interrupted and lost. On a success, it is deafened only until the end of the tick: spellcasting already in progress survives, but no new verbal component can begin during that instant.
The stone can shatter fragile glass and is audible hundreds of feet away. A creature already deaf or protected by complete silence is immune to its bodily effect.