misttaken

It seems to me like they might be the Elantrians who were dissolved in the Shard Pool. That would certainly explain how they ended up in the Cognitive Realm, at the least.

Ok. Crazy theory. We saw in Secret Histories that you need to have some Connection to a Shard in order to pick it up. Kelsier actually has trouble with Preservation for that reason, while Sazed (who has recently gained a connection to Ruin in addition to Preservation) is able to pick up both. My theory is that Hoid wants to eventually put Adonalsium back together, and is working his way around the Cosmere picking up a Connection to each Shard in order to do that. Spoilers for everything... Spoilers for WoR

On the other hand, the combination of Allomantic Atium and Feruchemical Steel is pretty much all you need if you have access to enough Atium. Throw in Gold compounding for good measure and you are all but unkillable.

What if they made a True Body with appropriately shaped bones? Would that work? Seems like it would be a much easier way to make super Kandra. Add in a couple of spikes and they would be terrifying indeed.

Couldn't they both be spiked? A Soother with a spike from another Soother would be much more powerful than normal, and extremely hard to detect. That being said, the hand holding thing is pretty suspicious...