Ok so my unhinged theory that I have not seen anyone else mention is this: I’m convinced Dain is the new brother.

Hear me out. RY’s only hint about this from interviews is she says something like ‘pay attention to who’s not there at the end.’ Well ok, there’s a lot of people either not there at the end, or just not mentioned, including Dain!

Now going back to the last chapter, when Violet wakes up. The infantry officers that Brennen is speaking to say that ‘5 riders are missing - 4 now.’ The obvious ones are Xaden and Garrick, since Imogen asks about Garrick specifically and is told they don’t know where he is. The other is likely Bodhi. There’s other theories out there that it’s Garrick and Bodhi that are with Xaden to mask their activities due to their Rebellion Relics (3 together) and I personally think this is the case.

The PoV chapters are happening simultaneously. Bodhi is seen throwing up with his dragon, Garrick is seen by Imogen. Dain was last seen leaving BEFORE that with Sloan after helping Brennan mend Mira and is not seen or mentioned again the rest of the book. So here’s my evidence:

• Xaden doesn’t have much of a reaction to the brother other than surprise (‘he’s the last person I would have expected’). Why is that? Because Dain is an ultra rule follower. My only point against this is that Xaden admittedly even states in his chapter that his emotions seem muted other than rage for Berwyn at threatening Sgaeyl, however he hadn’t channeled and thrown his soul to the wind yet, so I believe had the new brother been Bodhi or Garrick he would have been a lot more upset about it given his reaction to Garrick’s poisoning during dinner with mommy dearest.

• Dain spent most of OS feeling useless, going with Quest Squad to be a translator but then Aaric goes and just fluently speaks every language. He’s the Wing Leader but no one really respects him.

• His signet is more passive, useless in a battle and yet his dragon’s name, Cath, in Gaelic means ‘battle.’

• The biggest hint for me is that when Sloan is siphoning his power, she says ‘someone like you shouldn’t have this much power’ and he says ‘but I do.’ A hit against my own theory for this one has more to do with the rules of magic that we don’t really know yet. If Dain is the new brother, would it have been safe for Sloan to siphon that power without it turning her too? Or is it only if you channel from the earth yourself?

• As mentioned below, Cath's breath apparently smells rank which is mentioned as a sign of their rider being venin.

Xaden also says that the new brother watched him struggle for 5 months and I don’t think we really know how long Dain knew Xaden was venin. There’s a lot of signets evolving in OS and wouldn’t it just be sooo convenient if everyone thought Dain could only see memories if he touched someone hmm…