The Psijic Endeavor, often abbreviated as The Endeavor, and possibly, the Tri-Angled Truth,[OOG 1] is a method in which one can transcend mortal boundaries set in place by immortal rulers to achieve the state of existence known as CHIM.[OOG 2]
Contrary to popular belief, the Psijic Endeavor shares no legitimate ties with the Psijic Order save for a namesake, which are both based off of the Ehlnofex root-word, PSJJJJ, that being the ineffable and ever-changing action that is Padomay.[OOG 3][OOG 4] However, the Psijic mages were said to have their own interpretation of the Endeavor which they recorded in the Scroll of Adompha.[OOG 5] How exactly the Endeavor is achieved is not fully known, but it has been said that there is a shared "Old Way" which is taught by the Psijics, and a "New Way."[OOG 6]
The Psijic Endeavor was the original basis of the teachings of the Prophet, Veloth, whose "anti-laws" were inspired by the teachings of Mephala and Boethiah, who wished to show their followers the lies Trinimac had attributed to Lorkhan. Some sources claim that the teachings of the Daedra are not explicitly about the Endeavor, but that they merely form the antecedents of it.[OOG 2]
It is described as being a process of reaching glorious apotheosis where "time itself is bent inward and outward into a shape that is always new" allowing its users to acquire states of existence that reach beyond the abilities of even the gods. This state, which resides at the end of the Endeavor, is known as CHIM.[OOG 2] The immortal wizard, Divayth Fyr, had reason to believe that the Psijic Endeavor, or some similar process, may have played a role in the disappearance of the Dwemer due to their utilization of Lorkhan's Heart.[OOG 6]
The Dunmer associate Lorkhan with the Endeavor, believing that it was he who originally conceived the idea that the spirit realm was a prison, that being the reason he created the mortal realm, to be a new testing ground for transcendence. According to Vivec, Lorkhan was the first being to ever learn of, and utilize, the said process. Lorkhan first began his Endeavor by traveling to the end of the Aurbis, and then looking back upon it sideways, creating the infinite and godly image known as the Tower. After viewing the Tower, Lorkhan was inspired to create Mundus, a reflection of its own creators, so that others could learn of the Psijic Endeavor, and how not to fail it.[OOG 2][OOG 7] Vivec's teachings seem to imply that the Psijic Endeavor can be achieved through Lorkhan's Heart, as it holds a "secret Tower," which can only be seen by looking at the Heart sideways.