- There are (several) missable(s) in the game. - Jet's Humpty & Dumpty quest is missable, and has a time limit in which needs to be completed. - Strong-Willed Shopmistress' quests have time limit in which they need to be done (items become spoiled if you take too long). - A couple of Monster Book entries are missable (discussed later). - A couple of ARM parts are missable (discussed above) - A couple of Armors are missable (discussed above) - When Zed's cameo presents you with a choice regarding certain job he should be doing, you can choose to either track him down in various dungeons he'll escape to, or do the job in his stead. Note that if you do the latter, you won't obtain Doom Bringer ARM part. - Golden Nightingale - DO NOT SELL THIS ITEM!; otherwise you won't be able to obtain Hob & Nob weapon for Carol
Observation: I think that enemies go into Monster Book if you at least deal some damage to it. When I was in event battle with 1st Muspel, I didn't attempt to damage it at all, since I knew that it was a battle I can lose and still go on. But when 2nd Muspel was defeated, I have its entry in Monster Book. Again, this is just an observation and may not be correct.
There are a couple of one-time-areas and dungeons which contain regular enemies you should not miss fighting, otherwise they won't go into your Monster Book. The areas are: - FCB Network Studio (3 regular enemies: Stealth Stalker, Dullahan and Balazs). - Certain character's memory dungeon (3 regular enemies: Mu, Nosferatu and Archangel). - Locus Solus overworld, before entering Cradle dungeon (3 regular enemies: White Fear, Sekhmet and Graveshifter). These can be fought on Filgaia as well, but just take care of it while you're here. - Cradle dungeon (3 regular enemies: Assassin Force, Hyperion and Celaeno). - final area of the game; shortly before obtaining Exodus Orb the game warns you that by taking specific crystal there is a point of no return. If you take that crystal, save your game, and have no previous saves, you will be unable to return to Filgaia's world map, and thus never be able to complete your Monster Book (bonus dungeons, Sol Nigers, Golem-specific-enemies, etc.) unless you did so before entering final area of the game.
And now for few words on missable enemies: - Gehenna Neros: When you're fighting Gehenna Neros, make sure you wait enough time so that it divides into an original and a copy. Defeat the copy before defeating the original to get Monster Book entry for both. - Final foe's sword: when you fight the final boss of TF System: Tower O, make sure you wait enough time so that he uses GZ Nemesis. This will cause him and the sword to become separated. Damage the sword (critical strike from Dean will work) and then defeat the boss in any way afterwards (doesn't matter if boss grabs the hold of sword again). Same applies for second-to-last boss battle of the game. - Azhi Dahaka fused forms: in final dungeon you can randomly fight 3x different Azhi Dahakas (they all appear in same battle). If you cast Gather on one of them so that they're all together in the same hex, they will fuse into one of three forms (Azhi Dahaka leopard-form, Azhi Dahaka spider-form, or Azhi Dahaka bird-form). Defeat this form before it casts Isolate to have it go into your Monster Book. - Final storyline boss: depending on certain conditions, you will fight one of three versions of the boss. One is lv70, second is lv90, and third is lv100. I don't know yet what requirements are, so don't ask me about them - it is likely that whatever you do, on your first playthru you get to face-off against lv70 boss.