Something I've wanted to discuss, it seems probable to me that Dagoth Ur is Kagrenac transformed into the equivalent of a merger symbolically of Akatosh and Lorkhan hence Akulakhan or Akatosh and Lorkhan . The calling was known to use the dreamsleeve and Dagoth Ur is described as dream-sleeved inversion.

When the brass god was removed from the world its soul moved to the dreamsleeve but didnt die. A dead god dreaming because the tribunal as ALMSIVI destroyed the walking star or numidium. Kagrenac represents the enatiomorphic witness, his death the shattering necessary for the final step down subgradience after reaching AE.(props to the animuculi theory) The are seven heartwights each for a pure tone in musical theory or the earthbones minus akatosh and lorkhan or 9-2=7 also 2 can also be 1 and 1 or 11 also eleven plus 7 is 18 or a master.

My theory is that the sixth house were dwemer. That they literally recreated convention and lorkhans plans and created a mockery of the entire Godhead through the various earthbones plus time and space. That Dagoth Ur was the amanranth along with all the dwemer and they survived numidiums destruction but became mad. For further proof look to skyrim, when the ritual was recreated it grafted on to the nearest divine source and allows summon a shade.(very similiar to a heartwight) In morrowind that was the heart of lorkhan. Could it be ? Ive been searching for this answer for years.

Interesting, but i think i have to disagree right from start:

Book Sithis doesn't seem to back it up. Dagoth Ur, if anything, was fervent follower of Sithis. To him Anuiel and all it's pawns were merely enemies of Sithis and Lorkhan. In him there is no any sort of merging of two opposites, Dagoth Ur is heavily aligned to Sithis.

Sermons does hint that is Dagoth Ur's failing, his wrong walking path.

Center here stands for Sithis, Void that is tied down into middle of Wheel by gift-limbs of Aedra.

Witness has two options, or one. Alandro Sul is likely (and MK hinted at such) and i don't know if Alandro Sul is Dagoth Ur as well... In Five Songs of King Wulfharth there is Dagoth ur and Alandro Sul mentioned as separate entities, so that works against it. Then Ashlanders have story of how Nerevar told Dagoth Ur (his companion) to guard Heart, after he finds out Tribunals betrayal they try to kill him (but doesn't manage to do that). While Dagoth Ur is gone, Alandro Sul appears to Ashlander Tribes to spread his teachings.

Bit proof:

Dagoth Ur really seems to be close to Nerevar, Shield Thane as one might say. He's also known to be Wizard and Alandro Sul is said to be Son of Azura, Azura who embodies Mage constellation (along with Sotha Sil) in Chimer/Dunmer pantheon. So personally i take that as pretty convincing proof that Dagoth Ur and Alandro Sul are same personalities thus, Dagoth Ur has "just" become mad. Maybe because he became Witness, there is no marks of blindness or maiming in him, so maybe madness is his thing.

As for Amaranth: Amaranth won't be around. Otherwise one would have guessed that Vivec (of 3rd Era, he doesn't seem to be around in 4th Era) or Talos would have become Amaranth, but MK stated that if that would be the case then Mundus would be in their rear-vew mirror.

As for Dwemer i take it that they are gone, Just one remains and he didn't recon Sixth house as one of his own.

Something written in haste.