First, I really like your use of color! I like that each character seems to have their own scheme, which will help to make them recognizable :3
I also like how the clothing is both simple, but also detailed. If that makes sense? There's detail, but it's not so fraught with detail that it detracts from the characters.
I'm going to put my opinion for your questions (I'm not the BEST artist on the forum, but I thought I'd give my 2 cents :D)
Casthtis looks like his occupation is a fisher man. He looks kind and a bit doting for Zydre, who to me appears to be his partner or at the least a good friend. I'm not a fan of his hat, but the rest of his clothes seem very fitting.
Zydre to me looks like a village leader and possibly someone with magical abilities. She looks confident and kind also, which to me seems to be directed back at Casthtis. She looks like someone who gets things done.
Yurata is awesome! Love the colors (orange and blue are...um..complementary colors, right?) She looks like some type of sorceress or enchantress. The fish-bone jewelry tells me she may dapple in black magic, or may even have magic relating to the sea? She looks energetic and I personally wouldn't label her as a villain, but I could see her going that way. She looks nice to me.
Perperuna looks like a lightning warrior. They definitely look courageous, like they're ready to take whatever on. They also look like they came from a colder environs, since they've got some furs on. I'm saying "they" because I have long hair male characters, and I feel this character could be either male or female. I'm leaning toward female 'cause of the "a" at the end of their name. Either wya, I love the design!
Veles looks the most like a villian to me, but even then I could see him just being a mysterious wizard/enchanter. He looks like he has his guard up and is either himself untrustworthy, or is suspicious of others. I get this feel cause of his eyes, but also because of his hidden arm (maybe it's missing?) I also get that feel cause his magic seems to be spacial.
I like them all! I personally would make the line art a touch less sketcher, but if that's what you're going for, then you've done a great job!
I hope that's the kind of feed back you were looking for. If it wasn't, I'm so sorry for wasting you time!! I think they are good character designs, and just need to be cleaned up a touch (but, I'm not one to talk, considering my own own comic inking XD)