Shards of Roshar

[Julio]

“Three of sixteen ruled, but now the Broken One reigns.” 

Who are the three? Presumably Honor and Cultivation, but is the third Odium? It sounds as if the "Broken One(I assume that's Odium? Though, he's arguably not "broken".)" is not one of the three. "Three ruled, but now this other person rules." 

 

Also, I'd like to request that any Oathbringer spoilers be put under spoiler tags, even though they needn't normally...

[The One Who Connects]

7 minutes ago, Julio said:

“Three of sixteen ruled, but now the Broken One reigns.” 

One. Two. Make of these how you wish.

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Zenith

In one of the death sentence things it says something like three of sixteen ruled, but now the broken one reigns. Is this referring to the Shards on Roshar and if so, is the broken one Odium?

Brandon Sanderson

RAFO

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Outis

The line about three of sixteen reigned and now the Broken One rules. Did Odium follow three other shards to Roshar, or is he the third Shard?

Brandon Sanderson

Odium is the third Shard on Roshar.

[Calderis]

Combine these with the Stormfather's lament of "Odium reigns" to Kaladin in tWoK and I think we have the answer. 

Why Odium is called "The Broken One" is another question entirely.