The character of Lochru to me, has been hard to figure out the details of him. Before he was confirmed to be called "Lochru", I had a theory that he could possibly be Bruta - appearing to Merlin in a dream.
But I have two different scenarios!
Scenario 1 - Merlin's Grandfather (unlikely)The way he speaks to Merlin and the way Merlin looks at him really tells something! Merlin looks like he is about to cry. It looks to me, like a grandfather-grandson bond. And Merlin was said to have a 'vision' at the start of the series, and I think this is the vision! Him communicating with Balinor's father, his grandfather, and Lochru informing him of the darkness to come.
Scenario 2 - Wise-man Dying in the Northern Plains (likely)This scenario is perhaps more probable under the circumstances of the show not having that many twists... He could be one of the people who are 'disappearing' in the Northern Plains - because you can see that there's frost in the background, and you can see in the picture above that Merlin is looking down at him. So he could be dying. How does he know about 'Arthur's Bane'? Well, it's possible that he could be a wise guy who Morgana and Ruadan tortured to get information on Arthur's Bane. I haven't exactly put all the puzzle pieces together in completing this theory, but that is the basic outline.
I'd love to here your comments as well as your own theory on who Lochru could be... :D