|Stop! Drop! and Roll!|
Issue 0, Volume 1 of the Living Greyhawk Journal explains how neither Tenser nor Robilar really "fit in" in with what is now the Circle of Eight, and both left the group. Here is how I used Robilar in my campaign.
Eventually, after Tenser receives part seven of the Rod of Seven Parts from the players in a trade, he decides to go on a quest for the sixth piece. He forms a group of epic level adventurers to seek out the piece, which is held by a powerful pit fiend named Visciannix (see dungeon issues #130 and #135.) I described to the players a scene where they witness these incredibly powerful individuals outfitting themselves for an excursion into Hell, one of them being Lord Robilar, amongst others. It gave them a chance to interact with some of the flavor of Greyhawk, and forshadowed what they would soon become: power players in the realm of Oerth.
Ultimately, Tenser and Robilar will return in the final chapter of the Age of Worms to loan the combined pieces to the group as aid against Kyuss.