This one had a bit of a twist that the others lacked, for the Guardian, Rogan, has already found his Destined Mate. And lost her.
Reincarnated as Alison Blair, she has come back into his life. She knows what he is. She knows all about the Guardians as she works for them. With them and the seers that serve them.
Rogan is the only Guardian of the series that actual had reason to have qualms in being with his Destined Mate. He's found her once before, and she fled from him. She ran instead of choosing to love him despite her fears and died before she had the chance to change her mind. Now, back in his world, five hundred years later, Rogan can't bring himself to trust that she won't do it again. Nor, trust himself to survive losing her again.
I didn't care much for the end. Of all of them, Rogan was the least of which that deserved such an ending. Santos should have had this ending. Even Kieran having it would have made more sense. Hell, Alison should have had Julie's fate. So a little switch-a-roo there and all would be well.
Still, yay for the Irishman!