I've updated Petronius' character sheet with small details: appearance, height, weight, confidence, wizard's sigil, equipment and combat stats. I'm not fully satisfied by his personality traits, but I may wait until we begin play to update them, based on how the character feels in play.
Note that I've left the last year before the saga starts undefined, to adjust based on what we decide to assign as last-minute tasks for the covenant set-up. At worst, I can always say that he spent most of that last year scribing texts for the library.
Otherwise, he's ready for play. I'll keep adding background pieces as inspiration strikes. I know that I'm probably putting too much details in those pieces, but I figured anything stated there (particularly regarding the covenant of Irminsul) may be of use for the saga.