Rather bizarrely with this trophy, it didn’t actually pop for me until I’d used Ancient Magic a few times. When you get Ancient Magic, at the end of “Welcome to Hogsmeade,” ( and ) and use it on the troll, that seemingly didn’t count. Even when I used it on the next enemy, it didn’t register. It wasn’t until the third enemy I used an Ancient Magic attack on did the trophy unlock.

Hopefully it won’t be as buggy for all you out there. You’ll no doubt use Ancient Magic a lot, so it’ll pop eventually… surely!