Deras öde avslöjas långsamt under nästa serie, böckerna Wax and Wayne . Resultatet är att de flesta var underjordiska och överlevde därför.
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Kandra
Once he was done reorganizing, Harmony guided someone back into the kandra homeland caves and started putting spikes back into bodies. A majority of the kandra, including two characters we are familiar with, TenSoon and MeLaan, survive with some basic holes in their memory, due to the spikes being gone so long. Of the rebel kandra, no mention is ever made again, so possible they were left out of this rescue. Kandra show up explicitly again in Shadows of Self, but they're around before that if you're looking.
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Koloss
Most of the Koloss were incinerated, but Human and his band were underground. Per Word of Sanderson, Harmony took pity on them and altered them to be able exist on their own. They are only directly seen in a short story (published first in a Mistborn Adventure Game supplement, then in Arcanum Unbounded), titled Allomancer Jak and the Pits of Eltania, and haven't yet shown up in the main series of books. The story contains enough pulp to start a paper business, but according to the snarky footnotes the depiction of koloss is close enough to reality. Koloss have gender now and can have babies, although these offspring are definitely human, yet pick up some koloss traits like skin-tone, strength, and temperament (leading to the term koloss-blooded). They also have a little more self-awareness, although still fairly violent, and they keep a basic tribal society. True full koloss are still made through Hemalurgy, using old preserved spikes. They seemingly only convert volunteers this way, whether their children grown or a rare outsider, and send away any koloss-blooded adults that refuse this.
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Marsh
Marsh I think is the only creature that wasn't explicitly underground, but either he made it to a cave or his abilities let him survive. He reappears at the end of Alloy of Law, perfectly fine after centuries. Per the author, he still has that bag of loose atium Ruin had him grab from the kandra, and he has enough abilities to use it to Compound his age and stay alive, although we're not given any clues as to when it will run out.