The Sage has known Groo and his family ever since he was a boy (Groo, that is). He has always been there for them, ready to spew out relevant advice in all italics. Many times issues have a short Sage story at the end, as a filler. He usually appears to couch a Groo story as a relevant anecdote. He's really not as wise as you think, it's just that we're always comparing him to Groo.