As for how powerful or adept he is with his skills, Jace is perfectly capable of:
- Reading the thoughts of others both passively and aggressively, dominating another person's mind completely, rewriting or erasing memories entirely, implanting or withdrawing memories from another's mind; and, with a bit of time and work, learning another person's skills simply by copying them directly from their mind, absorbing languages, physical talents, and the like as if they were his own. He has to see the person to able to use his powers, however, and he can't project his thoughts as far as other telepaths of his caliber can in other canons.
- Creating lifelike, near-perfect illusions, become invisible or intangible, summon up elemental beings attuned to the air or water, shapeshift, counter or redirect spells, control water or ice, manipulate a person's perceptions, create powerful defensive personal wards, manipulate objects via telekinesis, and fly, albeit for short distances. Canonically -- and theoretically -- he can also use a bit of White (Healing/Defensive) and Black (Death/Necromancy) magic, but is nowhere near adept enough to do so on as grand a scale...if at all. He certainly won't have enough mana for it!
- In the City, this skill is largely irrelevant, as the Deities would not allow it to happen.
- Sensing magical or supernatural energies nearly a day after they have been used or summoned up. He is extremely sensitive to the occult and can easily perceive ghosts, illusions, summoned spirits, and the immaterial, as these are all things that relate to his main field of magical study.