If you listen closely to the dialogue that ostensibly Corvo is recalling being said to him in happier times, she says "When you are near, my heart is at peace. Hurry home."
There's a good chance it was more than a protector/ruler relationship between them. Otherwise, why not just disappear (besides the fact that there'd be no game

)
As far as the Outsider, he appears and deals with people who are important to the fabric of the world's workings. An example of this is Anton Sokolov, the official scientist for the people on-high. He also painted a portrait of the Outsider iirc. He might be appearing to Corvo because the murder of the Empress has shifted the balance of Dunwall and the world at large too much, making him a more benevolent form of neutral party. There's no indication of his motives really at the moment and there probably won't be until we play in October. Strife found out though that as we play we can visit his shrines where he comments on our actions.
Just a little more than nine weeks to go.