Based on the first Mistborn trilogy, it seems that unlike Allomancy, if you were a Feruchemist, you were able to use a Metalmind made of any metal. However, in the Wax Wayne trilogy, it is clear that most (if not all) Feruchemists can only tap into one Metalmind.
Was Feruchemy always like this - that it was possible to only have one power? Or did Sazed/Harmony change the rules when he recreated the world?

2 Answers 2


There are a few major factors at play here.

The first is the weakening of the allomantic bloodlines over time. By the time the Catacendre happens, it's implied that Spook is the only remaining Mistborn; and he is a standard weaker Mistborn, unlike Elend who was a full Mistborn due to the Lerasium bead. Source

The other major factor is the mixing of bloodlines. Before the Catacendre, Terris seem to be regulated pretty highly in terms of their breeding and mixing with the general population. This made it highly unlikely that the Terris would have bred with someone who had a strong enough allomantic bloodline to produce a ferring/misting combination.

Brandon Sanderson has said that you cannot be born both a full feruchemist and a full allomancer; there is too much interference between the powers. Ferrings were not possible before the final empire either.source

It's not really clear where all the feurochemists went at the time of the Catacendre, but we have not seen evidence of them in Era 2. I've seen speculation, and personally subscribe to the theory that in the Terris community, they still have full feurochemists somewhere. Just like during The Lord Rulers reign though, they are able to keep it a secret.

From the story, I don't see anything that definitely suggests that Harmony intervened to cause this situation. It makes sense that it occurs naturally, but I could also understand Harmony doing this on purpose, especially with the Ruin aspect of his powers.

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    I'm had thought Sanderson went on record that Harmony tinkered to keep things calmer and not have so many god-like humans running around. Can't find it now though.
    – Radhil
    Commented Oct 24, 2018 at 0:02
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    @Radhil I thought that at first too; but everything I can find on 17th Shard suggests he just let it run it's course. The lack of Mistborn makes decent sense with the narrative. The lack of full Feurochemists is a bit suspicious; but I think there's still a small chance some are hiding. The Terris seemed to be really good at breeding them in secret.
    – JMac
    Commented Oct 24, 2018 at 0:34
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    where did you get the idea that spook was a weaker mistborn? lerasium is a piece of preservations essence so if preservation (or harmony) made someone a mistborn they should be full power
    – Antheloth
    Commented Dec 24, 2018 at 12:33
  • @Antheloth If Preservation (or Harmony) made someone a Mistborn without Lerasium they would have control over how much power they can provide. In this case, we have at least one (but I believe multiple) "Words of Brandon" saying he was not full power. wob.coppermind.net/events/…
    – JMac
    Commented Dec 24, 2018 at 14:20
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    @Stormblessed No, the Lord Ruler was a mistborn and full feruchemist. He was only born a full feruchemist though. He was able to give himself full mistborn powers (possibly more than just a single Lerasium bead even, his allomancy was very strong) when he took the power of the well.
    – JMac
    Commented Jun 16, 2019 at 3:26

The reason for the diluting of the genes for feruchemy is because the remaining steel inquisitors went to the Terris Dominance and killed all the Keepers they could find. It's commonly held that, by the time of the Catacendre, Sazed was the only full feruchemist left alive.

However, the Terris people still had the genes for feruchemy, just in a more diluted form, and after the Catacendre, they started interbreeding with outsiders, leading to a further dilution of the genes, resulting in ferrings.

You can read all about it on coppermind.net/wiki/Feruchemy. There's a history section that details all of this.

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    Could you edit in some relevant information (quotes) from the link? Or better yet go to the source material (books) and get some supporting quotes from them to edit in.
    – TheLethalCarrot
    Commented Sep 19, 2020 at 6:59

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