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Source Core Rulebook

You can throw this stone as a ranged attack with a range increment of 20 feet. When it strikes a hard surface (or is struck hard), it creates a deafening bang that is treated as a sonic attack. Each creature within a 10-foot-radius spread must make a DC 15 Fortitude save or be deafened for 1 hour. A deafened creature, in addition to the obvious effects, takes a –4 penalty on initiative and has a 20% chance to miscast and lose any spell with a verbal component that it tries to cast.

Since you don't need to hit a specific target, you can simply aim at a particular 5-foot square. Treat the target square as AC 5.

Alchemical Power Components

Source Adventurer's Armory

While they are effective enough on their own, thunderstones have useful interactions with some spells.

alarm (M): If cast as a mental alarm, you may have the spell activate a mental and audible alarm. If cast as an audible alarm, the alarm is as loud as a thunderstone and affects creatures in a 10-foot-radius spread as if a thunderstone had detonated there.

glyph of warding (M): Creatures that fail their saves against a blast glyph are also deafened as if by a thunderstone.

An alchemical power component is an alchemical item used as a material component or focus for a spell in order to alter or augment the spell’s normal effects. What follows is a sample of these effects using this item as a component; your GM may allow other combinations.

Spells followed by an (M) expend the alchemical item as a material component;

Spells followed by an (F) use the item as a focus and do not expend it.

In both cases, the alchemical item does not have its normal effect and does not affect any other parameters of the spell. You cannot use the same item as both a focus and a material component at the same time.

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