Dune Worm

Dune Worm is another early boss that tends to stump a lot of players in the early stages. And it's not hard to understand why. Dune Worm has 1800 HP, has multiple status immunities, favors fissure strikes (incidentally, this will always be the first thing he does at the start of the fight), and at this stage of the game packs quite the punch. (200 HP hits are nothing to sneeze at.)

How you deal with him largely depends on your party setup. Just to be clear though, unless you visit this place later in the game when you've already developed some more advanced armor, from a defense standpoint it is very difficult to stop fissure strikes from being a problem.

But there are two things that DO work on the Dune Worm, sleep and airwave. The only way to lay down sleep is to use headblow, which is not hard to spark, but does require that you planned for this. Airwave is actually much easier to do. Airwave will cut the enemies HP by 5/8 (and has a very high rate of accuracy on the Dune Worm), but is considerably harder to spark before the battle at this point in the game if you tackled this early because of it's relatively high tech level. (level 18) Luckily the Dune Worm itself happens to be the perfect candidate for sparking airwave because his tech level is exactly 18. So there is actually a decent chance you will end up sparking the tech during the fight if you didn't have it already. In addition, he can also be blinded and is not immune to mental effects. Id break, light ball, and other techs of this type can be helpful here.