Licht's real magic it brings up when he gets his Grimoire is actually Sword magic. These are little things that reactors seem to have a tough time noticing in the little details. I believe Patry is actually a boy, that is the real person who is inside William is Patry. Patry has light magic as he didn't get his grimoire, he was supposed to do so the day after the wedding. Hence when he resurrected inside William's body, he went to get his grimoire. Furthermore, William looks like Licht hence why Patry was confused and why he assumed the name of Licht.
We got a good bit of back story for sure concerning the Elves in all of this, as well as why "Licht"/Patry states that those are the master's swords and the master's grimoire when it comes to Asta. There was that subtle hint early on that LIcht wasn't who we thought he was.