Just wondering.
Well, Percy and Annabeth are 16 in that book, and Luke is about seven years older than them, so I'd say about—16 + 7 =—23 years old.
PoseidonEpicness45 wrote: I believe 18 or early 20s.
18? Wasn't he 19 when he met Percy?
It's literally on the Luke Castellan page.
Although he is considered as the series' main demigod antagonist, he died at age twenty three as the hero of the Great Prophecy.