Getting the final Airship

[Crossblades]

First off, you can't get any MK weapons until Fargabaad, which is over some mountains, which only the Invinclible can cross. There are two caves with spliting enemies, the Underwater Cave, and one in Fargabaad. the underwater cave is required to pass through to get the Invincible. The best way to get through is to use your classes with the highest skills, or if you have a Black Mage, blast them away with whatever is your highest spell. (Thieves are recommended for their high escape rate)

There's 3 caves. You forgot Cave of Darkness

And Thieves are useless because you can't escape when fighting these enemies