Nightblood is made of atium

[Eri she/her]

I was doing a Mistborn reread and noticed that Ruin sounds pretty similar to Nightblood. I mean, his favourite line is “Kill him”. And he sounds happy about it.

And I thought, with all the world-hoppers, it's possible that the sword is made from atium someone brought from Scadrial, or an alloy of it. It would explain his personality and maybe how a metal thing could be Awakened (maybe unusual metal helped a bit). And may explain the corruption of Breath – mixing two not very compatibile Shards might give weird results, I guess.

Or it's just simply homicidal. But in Cosmere, things are rarely as simple as they first seem.

Edited January 3, 2012 by Eri

[Argent he/him]

I think the reason given in Warbreaker is more plausible. Vasher explains that when Nightblood was created, he was given the Command to "destroy evil." Except, the blade wasn't smart enough to understand what exactly evil is, so it just wants to destroy everything.

[Eerongal he/him]

I don't know....that's quite a bit of atium (and thus, a portion of ruin himself) to move from one planet to another. I'm going to have to agree with Argent. It's more likely that his inability to understand "evil", yet ability to comprehend "destroy" leads him to have a very ruin-esque personality by its base nature.