These slender, chalky rods likely originate with the alien denizens of Leng, but to what purpose is not clear. Rods of Leng are typically found with 2d20+10 charges and can be recharged, but only on Leng.
First, the rod functions as a +1 club when used as a weapon. A creature struck with the rod must make a successful saving throw or be drained of energy, taking a -2 penalty to saves, attacks, and damage until they have slept for 12 hours. If a victim is struck a second time, they fall into a deep sleep and cannot be awakened for 12 hours. The first strike expends one charge; the second does not.
Second, the holder of a rod of Leng can converse with denizens of Leng in their native, alien tongue.
Third, once per day the rod-wielder can cast ESP and mirror image; each takes one charge to function.
Expending two charges discharges a beacon that attracts the attention of the denizens of Leng; there is a 25% chance per hour that a denizen will come to investigate after the beacon is discharged, using dimensional pathways known only to the denizens. The denizens’ reactions vary depending on the reception and previous encounters with the rod-bearer; they are not automatically hostile.
Finally, a rod-bearer can be attuned to the essence of Leng by expending three charges. This grants the bearer immunity to poison and the ability to regenerate 3 hit points per round against any kind of damage, for twelve hours. However, if the bearer regenerates more hit points than their full hit point total, their corporeal body dissolves into inert slime and they re-form, naked and alone, in the otherworldly realm of Leng. Denizen of Leng HD 8; AC 5; Atk 1 bite (1d3+lassitude), 2 claws (1d4+1); Move 12; Save 8; AL C; CL/XP 13/2300; Special: None. The complete entry for Denizens of Leng can be found in Monstrosities.