You are trained to attack with all four arms at once.
Benefit(s): You can attack with up to four arms during a full attack (potentially wielding two weapons in two hands each, up to four light or one-handed weapon in each of four hands, or one two-handed weapon and up to two light or one-handed weapons). Only one weapon at a time can be wielded with a primary hand; any other attacks are off-hand. If you wield a two-handed weapon in your off-hands, you apply 1-1/2 times your strength modifier to the damage.
Sandy Petersen’s Cthulhu Mythos, © 2017, Petersen Games; Authors: Sandy Petersen, Arthur Petersen, Ian Starcher.