portus termini - Ars-Archange/ars-pbp GitHub Wiki
The least we can say is that the relations between Cantus Arborum and Portus Termini are not the best.
The two covenants have been in conflict for years over certain magical resources in the Arelat region.
Things escalated when one of their mages, Gerbert of Bonisagus, decided to steal the young apprentice of Mordecus Grint, an Ex Miscellanea magus.
Since then, a few decades have passed, and relations between the two covenants have slightly improved. In fact, Cantus Arborum did them a favor during the last tribunal, and they currently owe a debt to the covenant.
Perhaps access to their Summa on Magical Theory?