The aldmeri view on this point is more edifying than other approximations to the possibility/limit duality, such as stasis/change, or worse yet, good/evil. Unfortunately, the aldmeri view does suffer under a bias towards the possibility-pole, as exemplified by this passage:
Which claims Auri-El to be the motive force responsible for the existence of other et'Ada. This can be immediately recognized as incompatible with the identification of Auri-El as the avatar of the possibility-pole. There is but one aurbis which is primal and every advent results from the application of a limit, like the form of a statue being carved from a solid block. Luckily, some altmer developed the intellectual integrity to recognize the contradiction in their belief.
Some still misunderstand PSJJJJ to be an actor in a drama who caused the Aurbis to happen but hasn't been heard from since. PSJJJJ is the carving of the block. Each cut is PSJJJJ and each sculpture is an Original Spirit. As we know, Lorkhan proposed the project that was the Mundus and enlisted other et'Ada to contribute, and there is a taxonomy of et'Ada depending on the degree that they participated in Mundus. From "Shezarr's Song":
There are the aedra that participated and the daedra that did not participate, but the waters are muddied when further examining the degrees of participation. There are the Earthbones that completely subsumed their identities into the Mundus, the Planets that linked themselves inextricably to the Mundus yet retain independent identities, and the Stars that began to participate but then withdrew. This is according to the traditional aldmer view that the Mundus is a prison in which et'Ada were either trapped or escaped, but the daedra frame it otherwise: cutting parts off. If the et'Ada cut parts of themselves off to form the Mundus, it necessarily follows that there exist remnant portions of the aedra outside the Mundus. In the altmer cosmology, only a subset of aedra - the stars, or Magna Ge, fit this mold. To see how the pattern applies to all aedra, let us consider the Convention - that most eventful un-time. The Convention was the occassion of the Magna Ge's departure, among other events - not the least of which are the removal of Lorkhan's heart and the birth of Sheogorath, about whom Varieties of Faith says,
The truth is that Sheogorath is actually the same being as Jyggalag, but cursed into madness. The "birth" of Sheogorath at the Convention must actually have been the cursing of Jyggalag - but why should the removal of Lorkhan's divine spark be causally related? The answer lies in that he is the "Sithis-shaped hole", or an un-star. The stars are holes created by the departure of the Magna Ge to Aetherius. The un-stars are somewhat unique, but the key element is this: departure. Sheogorath is counted among the daedra, but before the Convention he was part of Mundus. The entire classification schema must be reevaluated.
The hypostasis of all et'Ada is the division of unity into parts - identification of a self through circumscription, with an implied identification of the remnant. IS and IS NOT. Seen in this light, the "cutting-off" involved in the Mundus is neither exceptional nor mysterious (beyond the degree to which et'Ada are necessarily mysterious.) Thus each aedra known to us must be a member of a triad formed of an IS (aedra), IS NOT (daedra), and an original unity. This division is in the likeness of Anu contemplating himself by forming Anuiel and Sithis, and is the only true origin of any "new" et'Ada.
Mortality was the cornerstone of Lorkhan's design, set in place by the removal of his divine spark. This confirms that Hermaeus Mora came into existence at the Convention, and moreover confirms this for the rest of the princes since Mora is "one of the oldest." As for the beings which are the unities of aedra and daedra, only one class matches the description of having removed part of themselves from Mundus at the Convention: the Magna Ge, or the stars. The star corresponding to Hermaus Mora and Akatosh, the greatest daedra and aedra, must be none other than the greatest star: Magnus. This brings us back to the un-star of Jyggalag. Who might be the corresponding aedra? Jyggalag's sphere is orderliness and the precise procession of predictable phenomena. His mission is to constrain possibility. The matching ada who remained in the Mundus is the one that is "more a limit than a nature" - Lorkhan. Lorkhan's failure, which was his success, was mortality, allowing that which he created to trancend its creator and the undeniable predictability of a causal universe. When Lorkhan lost his heart, Jyggalag correspondingly lost his mind. There is not a clear candidate for the original unity of Lorkhan and Jyggalag, but there is reason to suspect it is the entity known as Lyg, or "the Void Ghost."
What might be the consequences of Jyggalag's return to sanity? It is probably one of a few steps required for the return of Lorkhan, though its unclear whether Lorkhan would want to be restored since he "failed" with full forethought. Should he do so, it is doubtful that the Mundus would continue to exist. Could there be some agency knowledgeable enough to know how to restore Lorkhan, nihilistic enough to desire it, powerful enough to effect the events of the end of the age, and subtle enough not to appear responsible? Thankfully, this is unlikely.