A Higher Being
I hypothesise that if energy, time and space (there can be alternative forces. However, i will leave that for now) are eternal, then it's possible that they'll give rise to an incorporeal intelligence that uses these forces to awaken.
I believe that intelligence first evolved during this setting, thus being among those eternal forces. During this state of affairs, it's possible that intelligence plays a role in making or directional the laws to entire universes to set a selected foundation of an experience it intends to have in this universe - i.e. ours being somebody's experience.
Working In Harmony
So there are two parts: Forces like time, space, energy, are eternal, which they gave rise to an incorporeal intelligence that is additionally eternal. The implications are Multi-verse and in a manner, fictional realism, since these intelligence's will create an experience they want to own in 'said' universe, and duality by us and these intelligence's, creating us first in our true kind, immortal, manifested as mortals having a specific experience.
The reasoning is where it's at... if there's an immortal intelligence, then it'd more than probably figure out mortality. Imagine an immortal existence; it'll shortly (or in an exceedingly long period) eventually go mad.
Will Immorality Lead To Boredom?
But, though it does not go mad, it will solely have one experience as one person. What's the most effective way to have multiple experiences? To form or manifest as a mortal. With a deadline of where you experience, die, then experience something else... or keep in your immortality for a while.
Now.. this is not much different than what we tend to do currently. Imagine your favourite movie. Now, imagine somebody created you, or hypothetically you're solely allowed to observe this film for the rest of your life as entertainment. Well... it'd quickly become your worst film, and you'd dread watching what used to be your favourite.