My thoughts are that it is hard to have an opinion!
The way the story is told makes it sort of distant, so you can't get to know the character very well -- we just know the things that happened to him. He comes across more like a figure from a legend, because we know the things he did, but we don't know anything about him as a person. He's a king, he defended his kingdom when people attacked, but failed, and the southern kingdom rescued him and sent him off on a mission to explore a new world, which he accepted. That's not a character; that's a series of events.
For a more specific example, there's a really interesting detail when he arrives at the southern kingdom, and puts up a hood to hide his face -- the south and north have always been enemies. But I have no idea how Eric feels about this. When the soldiers from the south show up, we aren't shown any reaction from Eric, so I don't know if he's surprised and grateful for their help, or if he doesn't care about the North/South rivalry because he's too focused on the loss of his kingdom, or if he's a bit resentful of having to work with these people that have always been his enemies but feels he has no choice...... with what we've been shown of Eric, any of those options could be true. So that must mean we don't know him very well.
