The plaeryin bol was a creature capable of spitting deadly poison. It was used by the Yuuzhan Vong as a weapon, most commonly replacing an eyeball in its socket. It was notably used by Executor Nom Anor; the Yuuzhan Vong agent known as Dulac also used them. When used, the plaeryin bol's 'pupil' would dilate, and then launch the poison. It could be used accurately at a range of about 10 meters. The weapon was triggered by simple twitch of the user's eyelid.
After use, the plaeryin bol would slowly make more of its own poison, making it a reusable, inconspicuous weapon. It also had the advantage of causing semi-reversible damage. An antidote, usually kept in a small syringe inside a finger, was available to stop the plaeryin bol's normally fatal effects. This made it a useful torture device, being used to force information from a victim in return for the antidote.
The disadvantages of the plaeryin bol included being rendered nearly useless and dangerous to its user when employed in the presence of water. If one dared, for example, to fire the weapon in heavy rain, the plaeryin bol's poison would, at best, be deflected by the rain and, at worst, be washed back onto the attacker.