I am writing an epic fantasy story that features a cast of adult characters (early 20s to early 30s), but features many flashback scenes where the characters are 13-18 years old. It made me realize I really have no idea how to write teenage characters in a non-modern setting xD

I tried to pick the brains of some of my favorite teenage characters from epic fantasy - namely Kvothe from the Name of the Wind and Vin from Mistborn - but I noticed that while these characters are technically teenagers, their individual experiences are both very adult. Come to think of it, I really can't name a lot of teen characters in epic fantasy that live like teens.

I think the language is part of what has me stumped. Fantasy vernacular tends to be a lot more archaic than modern vernacular, but the dialogue of young people is going to differ vastly from that of adults.

What do you think? Have any tricks, or examples of well-written teen characters in fantasy that feel like regular teens?