The extra areas part of the postgame is a neat concept but my god are some of these bosses for the light pillars insanely weird and kind of unenjoyable. Is it me or is boss balance in this game kind of bad? There seems to be a weirdly large amount of bosses that are really difficult to damage even when you have insanely overpowered people on your team (Nitori).
Yeah, the main game's postgame bosses are probably the hardest ones in the game. I SHK cheesed The Great "C" to death to skip its duplication entirely, but mainly because I couldn't get a more consistent strategy fighting it normally. The Second Sun wasn't too bad (although I did empty the party of nonessential members to minimize the hassle of Time-Space Warp), but the Guardian of the Crystals has my vote for the hardest boss in the game, nothing contests that. You can definitely defeat it at challenge level, but it's pretty grueling. Took me about 20 minutes accounting for the frame rate loss while recording, but a large part of that was because I used Tenshi as the sole attacker throughout the entire fight. This is definitely one fight where you want multiple attackers due to how much MP you have to go through.
Wind Crystal has very low HP and defenses and can be taken out in a couple turns, but has high EVA so you have to be sure to use either high ACC attacks or have ACC boosts like Momiji's 50% boost to deal with it. My recommendation is taking it out first due to Calming Scent. If it gets a turn there's a very real possibility it'll just use that a couple times and then the Guardian of the Crystals can use Dark Star, which is pretty much a party wipe. Earth Crystal is susceptible to PAR and Water Crystal is susceptible to SHK, those two can be disabled for long periods of time provided that you have the MP for it. As long as you can prevent them from acting, you'll only have to deal with the Guardian of the Crystals and the Fire Crystal. Should be able to eliminate at least one of the Crystals this way. Water Crystal's Shredder is pretty dangerous this early in the game since buffs are vital for damaging and survival, so this one gets preference imo. Earth Crystal would be next for the healing. Guardian of the Crystals goes berserk if it's the last enemy standing, so defeating it before defeating the last Crystal is vital. That leaves you having to survive the attacks of the Fire Crystal throughout the entire fight.
Water Crystal has high overall DEF/MND, but if you debuff its defenses you can damage it fine. Earth Crystal has low DEF and high MND, while Fire Crystal is the opposite. Earth Crystal is also very resistant to non-SPD debuffs, so you'll definitely want to target its DEF or use defense-ignoring attacks on it. Fire Crystal's DEF is easy to debuff though. Make sure not to debuff Guardian of the Crystals too much, that'll trigger Dark Star too. It uses Dark Star when its combined buffs are at or exceed 150%, or combined debuffs are at or exceed 75%. As far as equipment goes, 3x Grand Master Breaker Title is your best option in almost all cases, but realistically you probably aren't going to grind for that on every character. Cyber Elf Grandie and Star of Elendil work out too. Fight mostly involves tanking MYS/DRK attacks, with primarily FIR targeting the first slot (Fire Crystal does have a potentially dangerous multi-target attack though). The other Crystals have weaker attacks, use fewer offensive attacks with their turns (particularly Earth Crystal), and can have their turns delayed easily (besides Wind Crystal which should be defeated rapidly), so their attacks are of less concern. Not to be ignored entirely, but the main offensive threat comes from the Guardian of the Crystals and the Fire Crystal. The Fire Crystal is the most dangerous to your first slot due to Crimson Lotus Fang and the highest attacking stat between all of the enemies, so FIR resistance is more important there. MYS/DRK are more relevant to the other party slots.
Another thing you could do is take out the Fire Crystal before the Earth Crystal, but then you have to spend more time PAR locking it to mitigate/negate its healing, since you have to leave it for last. This would be more complicated and luck reliant, but means taking less damage from the Fire Crystal, and the Earth Crystal is less dangerous alone than the Fire Crystal.
