Sibling's Heart

[+Child of Hodor]

Quote

“I will lead a team into the tower,” Raboniel said, “then secure control of the Sibling’s heart." RoW Ch. 14

She is talking about the gemstone pillar at the center of Urithiru, how it has been used a power inhibitor against the Fused in the past, but she thinks she can flip it around to only inhibit Radiants of the 3rd ideal or lower.

Doesn't this make it sound like the Sibling is Urithiru or at least it's core? I've seen people speculate that it could be the case, but this lend some support to it.

The Sibling is described as "slumbering" or sleeping by some spren including the Stormfather,  some spren have told Navani it is a permanent slumber. Others describe the Sibling as dead. We know the Sibling is a spren.

The vein-like hallways add to the idea that the pillar is the heart and light is carried from it to the rest of Urithiru (see the picture in this WoB https://wob.coppermind.net/events/406/#e14227). The pillar is the heart of Urithiru, The Sibling is needed for Urithiru to work. Urithiru has some things that work, like the air pressure, while heating to allow better crop growth is not possible right now. The tower is kind of in sleep mode, some basic functions still work, but a lot does not. It really seems like the Sibling turned itself into Urithiru or into the one giant fabrial (as Renarin described it) that makes Urithiru work. 

It would explain why Urithiru is OK to walk on according to Szeth. Because it is actually a spren turned into stone or a stone-like substance and not normal hallowed stone. 

Arguments Against

The Sibling is a spren and spren do not have that much of a physical realm presence normally. We know spren can turn into objects, but we've only seen it done with bonded spren. We can assume the Sibling has been unbonded for a long time and even during the desolations there were probably times when the Sibling Bondsmith died without passing the bond on to someone else pre-death. This would cause some discontinuity and I would think it would cause problems with Urithiru. 

Especially if the Sibling were both the giant fabrial and the stone of Urithiru. If Urithiru became mist for even a second thousands of people would die. On the other hand, they are a Bondsmith superspren, they may have different rules.

The Sibling could also be in the gemstone pillar and we just don't see it in there because it is sleeping / dead. That may be why the radiants were unsuccessful in infusing the pillar with stormlight. There is no more room.

[Honorless he/him]

Well put, mate. Shallan's study of Urithiru's strata in particular really seems to hint at the Tower being alive. Then Renarin's statements like "it does being a city" and comparing Urithiru to a fabrial. It makes me wonder if the Sibling is an artificially constructed spren, so to speak? Like, they don't represent any natural phenomenon but were created for the explicit purpose of becoming a home base for the Radiants.

[garlick]

I've always said, urithiru is like a smart home. The sibling is the CPU controlling it. Stormlight is the power. Though dalinar could in theory power the tower, the reason a bond Smith always stayed in urithiru. But without the CPU to control the tower, the stormlight is pointless.