...Right.
(The feeling Leareth has isn't exactly hesitance, more just - recognizing the significance, and what it means that he's not especially hesitant to show Karal the innermost part of himself.)
Leareth was, as far as he knows, born more than 1800 years ago, in Predain, a kingdom that no longer exists. His name was Kiyamvir Ma'ar.
He doesn't remember his childhood, exactly, just memories-of-memories, now whittled down to the bare fact that certain events happened. He was, he thinks, from a semi-nomadic herding people, and by the time he was reaching adolescence, conditions had gotten...very bad. He knows that his clan practiced infanticide, and that - there would have been a sister, one year, if they hadn't been already too close to starvation by the time the baby arrived. He knows that his father died by violence, and his mother in childbirth. He knows that he was different – mage-gifted, and...different in some deeper way. He doesn't remember being that child, not really, except as a formless emotion, the sense that, for all that he hadn't yet known anything different, he knew that this wasn't good enough.
Ma'ar left. He doesn't think he knew, at the time he left, where he was going, just - that if he stayed, nothing would ever change, and something had to.
The first memory that can really be called that is of Urtho's Tower, in the neighboring kingdom of Tantara. It's a memory consisting more of emotions than of anything more concrete - it was a place of wonders, of incredible magics, of books and learning, and it was a place where he never really understood any of the other students because they had grown up safe. But he does remember standing on a high balcony, looking at the stars - so many lights - and then at the ground, the bustling wealth of Tantara spread out in the darkness. Fewer lights than stars, but - still so many, and there could be more. He could take what he learned there, and bring it to Predain and fix it, and - and then to everywhere, because by now he knew there was an entire world. Maybe it should have seemed more daunting, to leap from fixing one country to fixing an entire world, but he thinks it wasn't as daunting as leaving the plains of Predain in the first place.
He made a promise, there at Urtho's Tower, that he wouldn't stop until everything was fixed and everyone had the safety and wealth and wonders of Urtho's Tower.
(Later, though he thinks not very much later, he realized it would take a lot more than one human lifetime, and began searching for a magical solution to immortality. He found several. The one he's using now was - a last resort, a final backup that he thinks he was only willing to countenance because he shouldn't have needed it. But, unfortunately, events went - differently than how he had planned.)
Ma'ar studied at Urtho's Tower until adulthood. He was, he thinks, reasonably close with Urtho - only one of his students, but a particularly brilliant one. He knows he very badly wanted Urtho to be proud of him, and...he thinks that at least sometimes, Urtho was.
And then he left, now a young man, and returned to Predain. Again, what he remembers here is unclear and mostly in emotional impressions. He remembers that Predain was a rougher culture than Tantara, living closer to the edge of violence - and he knew it wasn't the end state, wasn't what he wanted to build, but it made sense to him like Urtho's Tower never had, and he knew how to work with it. He remembers being impatient, hungry, frustrated that the best plans he could come up with to increase Predain's wealth and stability - and to improve the lot of the desperately poor regions bordering on Predain - would take decades to pan out. In hindsight, "decades" was an incredibly short timescale to be working on, but - he was young.
Ma'ar knew how to navigate Predain's culture and politics, and rapidly had the ear of the King, but - evidently he was lacking a lot of skills related to international relations, because - and it seems obvious now, but it really wasn't at the time - Tantara's King was alarmed by Predain's expansion, and Urtho had always been disturbed by political ambition, and - he doesn't know what happened. The records are gone and any memory of it is lost in fog. But, one way or another, the two kingdoms ended up at war.
Predain was winning. Ma'ar was - good at waging war, and Tantara had been at peace for over a generation and had no idea what they were doing. Leareth...is still pretty sure that Ma'ar tried to negotiate for peace. It's not as though he wanted to conquer Tantara, when Tantara had been stable and prosperous and doing fine.
Whatever he tried, it wasn't enough. He learned, too late - pieced it together after the fact, really, when he woke up in a teenager's body in a devastated world - that Urtho had weapons of incredible power, and that Urtho was willing to wield them, not just to send after Ma'ar in Predain, but to destroy his own Tower and everything he had built before it had any chance of falling into Ma'ar's hands.
(Leareth doesn't think that Urtho meant to set off the Cataclysm. It seems more likely that part was a miscalculation. But whatever the intentions, what was left afterward were two craters and a swath of unlivably damaged territory between them. He has only guesses at how many people died, but...it was in the millions. It might have been tens of millions.)
...And Leareth wasn't among them. He had taken just enough precautions, and his last-ditch contingency worked even when all of his other immortality setups had been destroyed. He was, for better or worse, one of the few survivors of a final escalation that he - may not have intended to push Urtho into, but that was still causally his fault - and he had made a solemn vow on the stars to fix everything, and learned the hard way how badly it was possible to miscalculate, and -
- he wasn't done. It's only the beginning of the story - Karal will learn a lot of the rest along with Leareth, there are huge swaths of his life that he has only the vaguest inklings of and he needs to spend a few weeks with his records, catching up - but that's the core of it.
(- never to die - never to give up - never to walk away -)