Eventually when Sebastian Sallow does Dark Magic, Ominis Gaunt asks you to inform him if Sebastian does anything else with Dark Magic.
Where can I inform Ominis that Sebastian has done Dark Magic again? Where can I find Ominis to tell him? Is it possible to tell him?
Or do I just need to continue with the story and eventually it'll come out to Ominis?
Play through the game a bit further and it will be revealed to Ominis, without any other intervention needed from you.
Shortly after finding Salazar Slytherin's book, you and Sebastian will go to a cave to try and find an artefact to help save Anne. Ominis follows you into the cave and discovers Sebastian and you have continued using dark magic. Soon after this, Sebastian's continued use of the dark arts is revealed to his uncle when he uses an unforgivable curse against a goblin during the fight in Feldcroft.
