PL-37 was a protocol droid in the service of Lord Toat of the Trade Federation. It was destroyed when Sol Sixxa sunk the Syren. Nym later recovered its head, and Jinkins was able to discover valuable information from the droid's "brain" about the cloaking device Sixxa had stolen.
PL-37 was created to serve Lord Toat onboard the Syren a Trade Federation when Toat was killed in front of was attacked by renegade pirates lead by Sol Sixxa. After Sol Sixxa stole a prototype Cloaking device from the Liner and sunk the ship where every Droid from the Battle Droids to PL-37 whose head was severed and landed on the bed near the ship.
The Droids head laid at the place for over a month until it was recovered by Nym, who was hired by Loreli Ro to track down and stop Sol Sixxa. While surveying the damage done to the Syren he found PL-37 and, after his encounter with a Relix, brought it to his ship, the Sunrunner, for Jinkins to work on. Despite a cracked brian case, the Bith managed to get the Protocol Droid to speak again in which it expressed about a prototype technology but it burnt out before anymore information could be extracted.
Unbeknownst to the party the droid's powering up was picked by Trade Federation forces lead by Harro Ruuk, who was on the Syren when Sixxa had sunk it, and sought to recover the cloaking device for himself. He was then able to track down the Sunrunner, waiting for both forces to and then secure the ships while both forces were exhausted. Ultimately the battle ended with Nym destroying both ships by colliding the Sunrunner with the Revenant. Nym would meet up again three weeks later to forge a new alliance with Sixxa on the Invisible Island, which housed multiple Stygium crystals, while holding PL-37s head.
PL-37 displayed standard characteristics of Protocol Droids in particular fear of violence. It also displayed fear of Pirates.
When recovered by Nym and reactivated by Jinkins it wasn't willing to cooperate immediately to their questions.
- The Complete Star Wars Encyclopedia