This is part of the main story - not missable. Here are some points to get you through the fight. This fight can be super easy hinging on one key factor - the bunk Boggled caused to him.
- The Fire Giant has 16000 HP at level 10. Once the battle rotation is complete, he will do a single fire blast to someone for about 1000 HP of damage and may cause overheating for additional damage to the character at the start of the turn. This was against the group which was all at level 8 with HP in the mid to beginning 2000 range.
- He can get Freezing and Boggled bunks, immune to all others.
- Use all items at the start of the fight which would help special attacks land the bunk Boggled on the giant - BMO’s Golden Crossbow or any of Jake’s Twister specials has the ability on chance to cause Boggled. Items which will help land the bunk are Rotten Fish (increase chance on all enemies receiving bunk from special attacks) and Used Tissue (increase chance on a single enemy receiving a bunk from special attacks). This bunk is key to a super easy fight.
- Once he blasts someone with his cannon, he will spin around in confusion leaving his most vulnerable spot open ONLY if he has the bunk Boggled active at the time of his attack. This is the time to unload the biggest attacks on him. There is no most effective elemental attack to use against him - all of them are equal, no better to worst (unless he activated an orb,then worst). He takes massive damage when his back is turned towards the groups, so do the heaviest hitting attacks.
- If he is facing the group, he will use a buff on himself immediately after the elemental damage he receives - for example, an ice attack activates his ice orb for protection. Save these attacks until Boggled can be activated and he turns around.
- As a backup, go into the fight with BMO’s special ability ready to be used. This will help in a pinch to get all characters HP back (depending how low some of the group really are) AND add a random buff to help with the rest of the fight.
Well timed hits and the activation of Boggled bunk are essential to making this level 10 fight super easy and quick. Good luck!