When imbuing an item with power, the enchanter must use a complementary store of knowledge (or power) in order to guide his will. The complementary skill provides the spark of magic that the enchanter then blows on like an ember so it blossoms into fire. Complementary skills must be one of the following: Doctrine, Sing, Folklore, Ancient History, Obscure History, Ancient Languages, Astrology, Demonology or Empyrealia.
So you could replace Sorcery with whichever of those represents the style of the specific sorcerer.
I’d also make sure that you’ve got the Enchanting skill (BWG p260), of course!
Combined with Astrology, that really flavours what your enchantments look like.
We’ve also used a number of those complementary skills to better reflect what this or that Imbue looks like, and to get a feel of how the Enchantment is built.
If you’ve got the Burning Wheel Codex, then you can also have a look at p290-305 for more detailed information, but for your NPC, I don’t think you’d need to worry about it.