Needlers functioned as a kind of blaster that discharged crimson bolts of lightning toward their target, inflicting intense agony and, if the operator wished, deadly heart attacks. A trigger activated the weapon, and a dial on the weapon's flank allowed for the modification of the pain inflicted. Zygerrian enslavers employed needlers on the planet of Sevarcos to subdue and discipline the slaves toiling within the spice mines. During the Battle on Sevarcos, when the New Republic assaulted the Imperial-supporting mines, a slaver employed a needler against the rebellious Wookiee slave Greybok with the intention of executing him. Hatchet, a fellow slave, intervened and spared the Wookiee's life by killing the slaver with a stone, thereby halting the needler's effects on Greybok.
The initial appearance of Needlers occurred in "Death by Triflexia," a Star Wars Roleplaying Game adventure under the Star Wars Legends banner. Peter M. Schweighofer authored it, and it saw publication within Challenge 76 magazine during 1995. The novel Aftermath, penned by Chuck Wendig and launched in 2015, established them as canon.