The rarest of the Forsaken's enemies, these chthonic entities are the spirits that represent concepts that existed before the world was fully formed. As such, they have no place in reality and exhibit powers and motives beyond comprehension.
Originally imprisoned on the moon, some of them were able to escape during the first manned moon landing and now roam the earth.
The idigam are spirits without clear analogs in the physical world. While a cat-spirit is emblematic of a cat, and a hate-spirit cannot be other than hateful, these spirits did not have natures. This should mean death for a spirit, and yet the idigam have been able to thrive. Moreover, they were able to take other spirits (or living creatures) and assume their traits, which made them impossible to contain or kill. The only way to rid Pangaea of them was to imprison them on the moon, in a place devoid of raw material. The idigam therefore entered stasis, unable to mimic anything around them. As they have returned to Earth, however, many idigam have learned to "congeal" themselves, developing true Influences at the cost of some of their inherent instability.
All idigam are capable of shaping and manipulating Essence to one degree or another, but one of them, Gurdilag, was a prodigy. It maintained the formless chaos of its pre-banishment, but over its years in the lunar prison developed a horrible and exacting sense of curiosity. It wanted to know how other spirits and "spirit derivatives” (such as souls) worked, and the best way to do that was to observe them without all that meat in the way. So he learned to remove spirit from flesh. And then he learned to reattach them, and this permitted the idigam to swap out a human’s soul for a spirit. In this way, he created beings that, unlike the Ridden, could also be created from Uratha, the Su'ur and the Duguthim. Because of the Brethren War, the Uratha noticed the danger only when it was too late. Gurdilag was eventually defeated, but the danger of his discoveries remains.