I believe Asterion mentions that if the MC were to drink it, he'd get incredibly sick. Wether this is true or he's just saying it to keep the MC from drinking it because of something worse, is unclear.
There has been a discussion like that on the forum before. Personally, i concluded the wine would have a substance like ichor (gods blood) that's poisonous to mortals. Seeing as Asterion is a demigod, he'd be safe.
