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From Pathfinder #217: Death Sails a Wine-Dark Sea, which isn't enabled.

Hydra Head Club

ITEM 6
Price 225 gp
Usage held in 1 hand
Bulk 1
Category simple
Group club
Damage 1d6 bludgeoning

This spine and skull of a slain hydra has been picked clean by a carrion bird and crafted into this +1 striking club. In addition to its normal traits, the hydra head club also has the modular P trait, as it can be manipulated to cause the jaws to spring open. Even in death, its head twitches independently. The creature's famed regenerative powers are still present, despite the creature's death; if damaged, the hydra head club repairs itself at the rate of 1 Hit Point per minute, unless it has been completed destroyed.

Activate—Reactive Snap (attack)
Frequency once per day
Trigger You attempt a Strike as a Reaction

Effect The hydra head club snaps with a momentary burst of its former glory. Your Strike attempt deals an additional 1d6 damage. If your Strike misses, the activation does not count against the hydra head club's activation frequency.

Craft Requirements You must supply a skull and spine of a hydra when crafting this weapon.
Pathfinder #217: Death Sails a Wine-Dark SeaORC