Jeremy makes an appearance in "Wizard." He is very old, and he is one of the three Ultimate Wizards keeping the meteor from hitting the temple. He has been there the longest out of all the wizards. Finn takes his place when he becomes a master wizard. After that, Jeremy is shown being put inside a coffin and buried alive by Bufo, implying he may be close to death. Furthermore, it shows that Bufo isn't interested in wizards for anything further than keeping his village intact. This is a reasonable assertion in that there doesn't seem to be a good reason to bury Jeremy instead of simply freeing him from his post, even though he is clearly shown alive.
Jeremy wears an Ultimate Wizard robe. He is short, wrinkly, and has white eyes. He also has a white beard as long as his body, so it's possible that the older one is, the whiter their beard gets.
It's about time!