Well this is quite exciting. I'm genuinely shocked that Kethric is a character that's around. Based on this trailer it seems he's gonna be our main nemesis? That's an interesting choice from a story perspective. I think we probably lose our first battle at moonrise and get brought to Baldur's Gate to heal. The trailer made it look like the fight doesn't go well for us.
“Ketheric isn’t the antagonist, but one of three main antagonists that your party will need to contend with if you ever want to get those tadpoles out of your head (maybe even if you decide you don’t 😏).”
I’m not sure who you think this is, but I’m pretty sure it’s a original character new to BG3. I couldn’t find anything non-BG3 related about him.