Eternal life could be infinitely boring.

So Aaron thought while moving through space, tens of millions of miles away from Earth, towards transcendental civilizations. He wore a simple white martial arts robe, having long surpassed mortal needs. Oxygen, food, and rest were optional for him, while his heart could withstand eons of boredom.

He had reached his limit though.

After reaching the peak of power in the known universe, there were no obstacles to overcome. Throughout billions of years, he had tried everything there was to try, done everything there was to do, to no avail. In the end, he was a warrior through and through, forged in the Everwar, and only the desire to defeat a powerful adversary could hold his attention for long.

So, if he couldn't find a proper challenge in the known universe, it was time for him to look for it elsewhere.

He had said his goodbyes to his disciples and paid respect to his late family's tombs, and was now moving towards the unknown parts of the universe, which comprised two-thirds of it. Certainly, he would find a worthy opponent somewhere out there.

A sudden energy disturbance in the fabric of reality in front of him awoke him from his musings. Filled with curiosity, he stopped to observe the phenomenon, and shortly after, a panel and a portal appeared there.

The thin panel was white with golden edges and semi-transparent like a hologram, but its existence didn't seem to be connected to any electronic or magical device. It contained some text in Al'Tharyn, the Secret Language of the Universe.

[Extraordinary Writ]

You have been called to another dimension.

Help save countless people from an enormous tragedy!

After reading the panel, Aaron investigated the portal which looked like a mere door frame on the walls of reality, a silvery outline of light with a rounded top. Despite its simple appearance, it connected two different dimensions.

On the other side of it, he saw a large room with two people. The closest one was a woman wearing a black hooded tunic, gesturing with shiny hands and chanting words in a language Aaron didn't recognize. And at the end of the room, a man wearing a crown was sitting on a high throne. He guessed the female was the one summoning him, and the male was a king. From the way they were looking at his general direction, none of them could see through the portal as he did.

Both were incredibly weak, mere insects compared to his power, causing him to immediately lose any interest in the invitation.

Meddling in the affairs of short-lived weaklings brought him no joy. Their disputes were too easy to solve; whatever tragedy had befallen them couldn't justify the intervention of someone like him. It would be like using an atomic bomb to destroy an inconvenient anthill. Moreover, immortality had a way to mess with the perception of time unless one was invested in something. From his point of view, it wasn't worth it helping them just so they could die a couple of instants later. It would be even worse if he became invested enough to care about them, only to feel their loss shortly after.

He turned to move away from the portal, but froze when he heard something he never imagined he would ever hear:

The Universal Core of that other dimension was screaming in pain and anguish!

It was such a shrill cry that even Aaron felt his hair stand on its end. He had rarely encountered such distress even in his literal eons of life.

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Sheer reflex made him focus on the source of such suffering. Absolute Energy left his body, went through the portal, penetrated the fabric of reality in the other dimension, and searched for the scream. He had to fight the other universe all along, for his energy was an invading one. He spent over half his reserves before he reached the Core, and what he found there left him astonished.

The Core had been imprisoned!

A universe's most fundamental building blocks were its Laws and Energies. They originated from and returned to the Source, the Center of the Center, the Core.

That dimension's Universal Core looked like a lab rat locked into a Cage, with hundreds of thousands of syringes puncturing it, sucking its essences, and forcing it to do things contrary to its nature. The damage and stress it caused were such that in a few million years, that universe would simply implode!

Universal Cores had a kind of instinctual intelligence, and Aaron could feel the Core practically begging for help from anyone powerful enough to hear it.

While he had ignored the king's problem, he didn't think twice before deciding to help the Core. That was an issue worthy of him. It was also an exciting one because if someone had placed that Cage there, he would certainly have to fight against that someone too.

Only the special and inviolable rules of inter-dimensional travel prevented him from going through the portal immediately. Rules that paradoxically were only a problem because of his immense power, which was what allowed him to hear the cry for help to begin with.

Those like him, who used the energies of the universe to gain power and immortality, were known as cultivators. The stronger a cultivator grew, the more they became linked to the Laws of their universe, and thus the more dependent on said Laws they became. The essence of the cultivator's very existence changed completely and irreversibly.

Unfortunately, the Laws of different dimensions, however similar they may be to each other, still had fundamental differences that couldn't be simply ignored. The stronger a cultivator was, the more power he lost when traveling to another universe, since it severed their connection with the Laws of their native universe.

If Aaron went through the portal, he would lose much of his power. Furthermore, as his essence had already been altered by the Laws of his current universe, it would be impossible for him to grow stronger in the other universe, making him forever trapped in a body that was nowhere powerful enough to save the Core.

The alternative would be to allow the other dimension to give him a new body, something common to happen when a foreign being enters a new dimension. However, that would turn him into a mere mortal.

He had a decision to make.

On the one hand, he had been looking for a worthy opponent for ages. Now, it was being offered to him. He could almost taste the upcoming glorious battles already.

On the other hand, he would temporarily lose all his power. Fortunately, he was an experienced warrior, the greatest energy manipulator to ever live in his own universe, master of all the Higher Arts. Even if he turned into a mortal again, he would have no trouble fending against weak cultivators. Only after a certain level of power would people become an actual threat to him.

As long as he didn't meet someone too powerful at the beginning of his journey, it wouldn't be difficult for him to grow up fast enough to protect himself. He felt confident he could flee from the summoner and the king if needed, at least.

It was risky, yes, but it wasn't a terrible offer.

Aaron decided to do it. That said, he hadn't reached the peak by foolishly heading into danger. Before stepping through that portal, he would prepare himself.

He sat in lotus position — legs crossed and upright posture — closed his eyes, and used Absolute Energy to create a time-dilating cocoon around himself that made time run ten million times faster inside.

For one Earth hour, he meditated.

During that time, which was around a thousand years inside the cocoon, he focused on feeling and understanding the Laws, Concepts, Truths, and Energies of the other universe. With his power and experience, that's all it took him to determine the differences between the universes and adapt his techniques to the unknown dimension.

When he was done, he opened his eyes to see the king staring at the portal intensely and the summoner almost fainting from tiredness.

Aaron took one last look at Earth.

Time in the Milky Way ran differently from the rest of the universe; his countless years of life out there were less than fifty years on his home planet. Still, those few years had been enough for his entire mortal blood-related family to have died. There was no one there to miss him.

Then he looked at the rest of the universe, at the stars of the past visible from Earth.

His immortal family had long chosen eternal rest, while his direct disciples were already Prime Immortals, only one step below him power-wise. They could maintain the peace he had brought after the Everwar ended, even without his constant supervision.

At last, he looked back at the portal.

He could almost taste the upcoming glorious battles already. There was no better feeling in the universe than overcoming a mighty opponent. He would bring righteous death to whoever stood in his way as he moved to save the Core, and that's just how things should be.

He smiled and stepped into the portal.