Abilites.

[the_original]

Well, he was sickly; but it can be accurately assumed that in good health he'd be as agile and skilled as any other person his age. Though, considering he'd likely be schooled more in magic, while he could fight with his staff; likely he'd assume a more traditional support role and nuke everything with heavy spells. His Fon Master Guardians would be on the frontlines attacking up close for him.

That being said!

The only known skills he has are Daathic Fonic Artes, as learning them is a requirement of every Fon Master. It's not known how many there are, as we only see four.

Reading the Score on a greater level than the Order's usual Scorers.
Akashic Torment (It's not named persay, but this is what Sync calls his, and Ion is shown using the exact same attack at least once in game, and as an Mystic Arte extension.)
Curse Slot
Creating and Unlocking Daathic Seals (Ion is only ever shown unlocking them, but it can be assumed that he possesses the capacity to form them as well.)

As for traditional spells; Well, since the Fon Master was required to be a Seventh Fonist; it's likely Ion's magical pedigree lent to some serious talent with Fonic Artes as supposedly it's obscurely mentioned that Fon Masters picked in Yulia's Score were descendants of herself and the first Fon Master, Freyr Albert. However, nothing is shown or even hinted at in-game. So expect lots of Fonic Artes I find fitting, as every character has a motif to them in-game, and therefore other Spell Artes may be pulled from other games, and some may even be made up.

That being said; Ion will wield a collapsing staff in battle; it merely shortens into a cane when he wishes. Why? Canes are pimp. That's why.