Rio, Xan, and Silas are going to have an amazing love triangle
So we have Silas, in love with Xan. Rio, who's in love with Xan, but doesn't realise it yet (just run with it, okay?). And Xan, who's in love with both of them, but denying his feelings toward Silas because of his betrayal. But soon, Silas will redeem himself, and Xan will start falling in love with him again. They'll start a very secret relationship, and it will remain secret for exactly 20 pages before Kari walks in on them.
Because Xan is terrifying, it won't take much for him to convince Kari to keep it a secret. However, because she's a teenage girl, it'll take her all of two hours to accidentally blurt it out to Rio. Rio will then confront Xan about it, and in doing so will realise his own feelings for Xan. At Kari's prodding, Rio will eventually tell Xan, who will then start passionately kissing him. (At this point, everything may or may not transform into shoujo art style.) At this point, Aiden walks in on them. Xan, who is still terrifying, easily convinces him to keep it a secret.
But Aiden, being a teenage boy, will let it slip to Silas. Silas will then demand an explanation from Xan, who will admit that he loves both of them, and doesn't want to choose (you know where this is going.)
And then Rio, Xan, and Silas form a menage a trois and live happily ever after in Dell's Wind. The end.
The Blue King will eventually be defeated...
By the Power of Friendship
. Only when the five main characters bond together can they combine all of their powers to create a Flaming Icy Lightning Sword shot from Xan's bow and propelled by their love for each other. This will prove to be the deadliest weapon, and will lead to the defeat of the Blue King.
Xan and Rio are going to end up married by the end of the series.
Because... well, because. Look at them, they're practically married anyway.