Incapacitation

[yukikaze_yanagi]

As far as I know, incapacitation is random. I usually just spam the skills needed, and it goes off eventually.

I also hadn't heard of Ifrit's Horn being a breakable part.

not by a long hot. Every incap have a set of hp, then the limb is broken. Usually permanently, some may be temporaly, like great buffalo's legs.
Ifrit always had breakable horns, lower his regen. In time of lancers was part of strategy, later with thunderspam it wasn't needed.