How did the Lord Ruler live so long?

[Munazir]

I finished the final empire and I’m still confused on how the Lord Ruler lived so long and was so powerful. I know he used  feruchemy and allomancy and he made himself old for 3hrs every 3 days but shouldn’t all Keepers be able to do that 

[Frustration he/him]

30 minutes ago, Munazir said:

I finished the final empire and I’m still confused on how the Lord Ruler lived so long and was so powerful. I know he used  feruchemy and allomancy and he made himself old for 3hrs every 3 days but shouldn’t all Keepers be able to do that 

So Feruchemy on it's own in neutral, so you spend a hour a year older and can become a year younger for an hour as a result.

 

If you are also an allomancer you can burn your metalmind(where you store that attribute) and instead of(in the case of Atium) seeing the future, that investiture is used to make you younger. Basically what he was doing was making a new allomantic metal that only he could use, meaning he could get more youth out than he had stored in the atium.

[HSuperLee he/him]

As much as I understand why Sanderson included a scene of the Lord Ruler appearing old, I kind of wish he hadn't just due to how much confusion it caused. The Lord Ruler didn't have to appear old, he did so only because it allowed his body to better reflect the way his mind felt. Even when he appeared as an old man, he was still drawing a huge amount of youth from his metalminds to make himself almost a thousand years younger than what he actually was.

Frustration is correct in his answer. The Lord Ruler stored a small amount of youth in some atium a long time ago, probably something like a decade or so. Then he burned that piece of atium and, rather than getting the normal future sight, his allomancy identified the youth stored in the atium and was like, "Oh, youth. I know what that is. You want more of this? Okay." And then it burned the atium and produced more youth than was stored in the metal alone, resulting in a net gain of something like a century of youth, which the Lord Ruler immediately stored in another piece of atium. He now had his default age as the ability to make himself a year younger for a hundred years, or two years younger for fifty, four for twenty-five, etc. But then he took that piece of atium with a century of youth in it and burned that too, resulting in a millennia of youth, which he stored in another piece of atium. On and on he did this until he had enough to keep him in the prime of his life for a very very long time, and he stored all of that in one of the two bracers he wore on his arms. From then on he could slowly draw out the youth stored in the bracer as time went on to counteract his aging, making him youthful again. When he appeared old, he was simply drawing less youth from the bracers, and he only did that because he felt old and it made him feel better to look old. He had a kind of body dysmorphia thing going on with that. But that's basically how he did it.

[Primeival Chaos he/him]

He was compounding Youth. He Feruchemically stored Youth in some atium then Allomantically burned it. It's like he swapped the power source for the Feruchemical Youth from himself to the metal. 

[AquaRegia he/him]

Great answers, everyone.  I'll just add that presumably, anyone who has both Allomancy and Feruchemy with the same metal should be capable of compounding.

https://coppermind.net/wiki/Compounding

[StanLemon]

On 12/7/2022 at 2:06 PM, HSuperLee said:

As much as I understand why Sanderson included a scene of the Lord Ruler appearing old, I kind of wish he hadn't just due to how much confusion it caused. The Lord Ruler didn't have to appear old, he did so only because it allowed his body to better reflect the way his mind felt. Even when he appeared as an old man, he was still drawing a huge amount of youth from his metalminds to make himself almost a thousand years younger than what he actually was.

My personal in world headcanon for this is that he used it and his old Terris items to act as a release of sorts. To reminisce and just feel his age without any expectations and drink up the nostalgia of his old home