Tribunal Border (major hook) - The covenant is located at the collective border of three Tribunals (Rhine, Normandy and Greater Alps), with all having some claims to that territory and its vis sources.
Local Ally (minor boon) - The old magus had made a deal with the Telsberg family, providing some magic (perhaps even a minor longevity ritual) in exchange for their assistance and rights to build the covenant where it is. The family remains an ally of the Heir (and thus the covenant), though they might expect some occasional magical help.
Favors (minor hook) - If we want the three filii of the old magus to have a minor role to play in the saga we could pick this hook.
Site:
Aura (minor boon) x2 - I think an aura of +5 makes sense, considering the remote location of the covenant and the plentiful vis sources.
Poorly Defensible (minor hook) - The chaotic buildings and the fact that the covenant is at the foot of a cliff make it difficult to defend the covenant against mundane attacks.
Fortifications:
Manor House (free) - The main building.
Important Buildings (minor boon) - To represent the additional wings, the towers, etc.
Crumbling/Outbuildings (minor hook) - Several parts of the covenant are in poor condition. Plus, the covenfolk live in their own houses near the covenant buildings, adding to the confusing state. I don't think those issues warrant seperate hooks, so I would suggest combining them into a single hook.
Resources:
Vis Grant (minor boon) - This is how the Heir recruited the magi of the covenant, by promising them a share of the raw vis harvested by the covenant.
Right (minor boon) - Our main source of income is recognized by mundane authorities and secure.
Contested Resource (minor hook) - At least one of the vis sources is known to magi of the nearby Tribunals and they try harvesting it before we do. This could be taken multiple times.
Residents:
Peasants (free) - The villagers of Chastellion can be called on to defend the covenant.
Veteran Fighters (minor boon) - A small cadre of experienced grogs is the core of the covenant's defenders.