Ok, I think that there is a lot of speculation on the Shards of Andonalsium, but there is something going on.
Here is what Brandon Sanderson has stated in the Hero of Ages topic
Ruin and Preservation were not the only Shards of Adonalsium, though they are the only ones on Scadrial at the moment.
(Scadrial is the planet
Mistborn is on)
A manifestation of Ruin's gathered consciousness, much like the dark mists in book two. The lake was still around in Vin's era, but had been moved under ground.
You've also seen one other manifestation like this....
Such as...this?
The "lake" was barely ten feet deep—more like a pool. Its water was a crystalline blue, and Raoden could see no inlets or outlets.
If that's what you're hinting at...I never thought of the connection before! I just kept thinking of Aether of Night, and never thought of this pool at all.
Both are accurate, but the first is what I meant, as most people here don't have access to Aether.
The powers of Ruin and Preservation are Shards of Adonalsium, pieces of the power of creation itself. Allomancy, Hemalurgy, Feruchemy are manifestations of this power in mortal form, the ability to touch the powers of creation and use them. These metallic powers are how people's physical forms interpret the use of the Shard, though it's not the only possible way they could be interpreted or used. It's what the genetics and Realmatic interactions of Scadrial allow for, and has to do with the Spiritual, the Cognitive, and the Physical Realms.
Condensed 'essence' of these godly powers can act as super-fuel for Allomancy, Feruchemy, or really any of the powers. The form of that super fuel is important. In liquid form it's most potent, in gas form it's able to fuel Allomancy as if working as a metal. In physical form it is rigid and does one specific thing. In the case of atium, it allows sight into the future. In the case of concentrated Preservation (Lerasium), it gives one a permanent connection to the mists and the powers of creation. (I.e., it makes them an Allomancer.)
So when a person is burning metals, they aren't using Preservation's body as a fuel so to speak--though they are tapping into the powers of creation just slightly. When Vin burns the mists, however, she'd doing just that--using the essence of Preservation, the Shard of Adonalsium itself--to fuel Allomancy. Doing this, however, rips 'troughs' through her body. It's like forcing far too much pressure through a very small, fragile hose. That much power eventually vaporizes the corporeal host, which is acting as the block and forcing the power into a single type of conduit (Allomancy) and frees it to be more expansive.
(Lerasium added by me)
Readers have met four shards other than Ruin and Preservation.
You've interacted with two directly.
One is a tough call. You've never met the Shard itself, but you've seen its power.
The other one you have not met directly, but have seen its influence.
Something I noticed is that Ati pulls with his magic (energy lost)
And that Leras/preservasion pushes with his magic (energy gained)
Maybe we could use that to help find the other Shards?
I think it's safe to assume that the Dor is a Shard, and we met it when Raoden fell in the pool.
I don't know about the others. Possible canditates are:
Lifeless? ( I don't know who would power them. Maybe they gave people Breaths?)
Iridescent Colors (powering the returned)
Jaddeth (powering the monks of Dahkhor)
Maybe whatever powers the Smedrey Talents? (Alcatraz)
Others?
Maybe we will be able to figure out who Hoid is as well...
Zas