From PathfinderWiki

Source: Valley of the Brain Collectors, pg(s). 90

The result of a neh-thalggu absorbing a critical mass of mental energy, yah-thelgaad are even more efficient harvesters of power from brains. They hold a fanatical faith in the Ineffable Void, a cryptic mystery of the Dominion of the Black.1


The yah-thelgaad is a creature covered in spiky chitinous plates with a forest of tendrils on its 'face' and a sharp tail. Its back is adorned with six transparent blisters containing a green liquid.1


Once a neh-thalggu has absorbed enough thoughts and memories from the brains it collects, it enters a torpor and consumes its seven oldest collected brains. Over several days, it undergoes a metamorphosis into a yah-thelgaad. While yah-thelgaads can only store six brains (compared to a neh-thalggu's seven), they draw twice the power from each brain, and can collect the brains of non-humanoid creatures as well.1


In addition to their loyalty to the Dominion of the Black, they are also fanatically devoted to the Dominion's theology, which includes mysteries such as the Ineffable Void. High-ranking yah-thelgaads often become inquisitors or oracles to command their minions, and the most powerful ones also become mystic theurges to combine their own divine magic with the arcane lore of their collected brains.1

Yah-thelgaads often serve as supervisors of the Dominion's surgical and genetic engineers, pushing them toward horrific procedures. Despite their cruelty, yah-thelgaads seem to feel no emotions of their own, but instead experience them through their stolen brains, preventing enemies from affecting their minds.1


  1. 1.0 1.1 1.2 1.3 1.4 Mike Shel. “Bestiary” in Valley of the Brain Collectors, 91. Paizo Inc., 2014