Spoilers ahead. You've been warned.

In the Fuse scenario, Fuse has access to a boss rush mode. If you beat every character's boss before challenging the final boss, the final boss will be a super version. This guide is about how to beat these fights, as they are quite difficult, and there are not any guides as far as I know about beating them. Beating one super boss is a requirement for the Pushing Limits achievement. This guide is a work in progress.

• Your characters should have 800-900 hp and stats in the 80s or 90s. They should ideally have 150+ WP and JP for long fights. When Dullahans no longer give you stat-ups, you can train with big slimes in the Shingrow Ruins. Do not use bonus stat equipment when training, because the game takes into account your current stats, not base stats, when giving stat increases. Notable stat increasing equipment is phantasm, gilrandy, and power suit, which can help max things out once you hit the 80s and 90s.
  
  
• You can and should abuse NG+ mechanics to get additional copies of key items. I would advise not to think of anything as cheating, because these bosses are designed to challenge the most broken of parties. I personally think these bosses are fun and challenging regardless of how much you abuse the games mechanics. Most ultimate bosses are immune to stasis, but you can still use overdrive and stasis yourself at the end.
  
  
• That being said, if you want to challenge yourself, feel free. I personally have not used overdrive a single time in my playthrough and it's felt very rewarding. You could also try to do it without using any time magic at all, or without DSC and Tower. All of this is totally possible -- play the game how you want to play it. But remember that these ultimate boss fights are designed with broken strategies in mind.
  
  
• Bring lots of sanctuary stones. Boss rush doesn't heal between bosses. Consider going with a gunner+tower strategy to minimize sanctuary stone usage and preserve WP between bosses. You can easily farm stones by doing NG+ with Fuse and grabbing stones. Examples: Owmi dungeon (first treasure room) and IRPO arcane quest (dragon treasure room.
  
  
• Boundshot, shadow sphere, tiger rampage, sunder, clear water, and lifewave are some low WP skills that combo well together and are effective damage to help save resources for DSC and Tower.
  
  
• Most bosses generally have a structure of phases. After reaching a certain point in the fight, many of the ultimate boss' increase their damage and change their pattern to one of aoe damage spam. You generally want to make sure you have your most powerful attacks, like Tower, for this phase to burn the boss down before he burns you.

• Humans are generally the strongest characters you can bring to these fights. Most humans are interchangeable as long as they learn the stats and skills required. Every character can learn any skill eventually. The best humans are Blue/Rouge for huge tower damage and magic diversity, Emilia & Liza due to ease of learning DSC, Asellus, she can easily max stats with absorbs and learn magic heal, Gen who learns arts very quickly, and Red if he has Final Crusade.
  
  
• Mystics are notably useful for being able to easily max stats and use time magic. Time eclipse and time leap should be on every mystic you plan to use. The last two magic spells are personal preference. I like vitality rune, shield, or tower. They should also have mariche absorbed into their mystic sword for magic heal. There is an easy trick to absorb Mariche quickly by challenging Riki's boss in the boss rush room. The best mystics are Time Lord and Mesarthim, for life rain and time twister/overdrive respectively.
  
  
• Mecs are okay, they have status immunities and can get max stats more easily than other races. I would recommend against them because their damage potential is lower than humans and they have no good healing spells. T260G is the only notable mec since he has V-MAX.
  
  
• Monsters take a long time to develop their HP and their damage skills are usually not very effective. If you use a monster, I recommend making it primarily a healer with magic heal, life rain, and mighty cyclone (for combos). Notably good/usable monster forms are Dullahan, Black Dragon, and Kylin. I think monsters are the weakest characters in the game and you should only use them if you really want to challenge yourself. Most monsters are about the same, so pick what you like.
  
  
• An ideal team will consist of: Fuse (mandatory), a healer with life rain+magic heal, and three damage characters. Someone without a heal spell should carry a backpack for emergencies. One of your damage dealers should preferably have time magic. ​
  
  
• The team I used was Fuse, Emelia, Liza, Rouge, and Mesarthim.

• They should ideally have boundshot/guns akimbo for quickly killing boss rush mode. Boundshot combos with itself and is an easy high source of damage for low WP cost. It is also useful in longer ultimate boss fights, since you will likely run out of WP spamming DSC. Alternatively, you can replace boundshot with sword skills that can combo with each other. This will probably be lower damage/more WP than boundshot combos, but has the advantage of deflect and a slot for phantasm stat bonuses.
  
  
• Tower and high JP for is useful for burst damage.
  
  
• You should have DSC on 2-4 characters.
  
  
• At least two characters should have time eclipse and time leap, which can be either your humans or mystics.
  
  
• Optional magic that is useful includes Shield, Grail (single target status removal, Vortex (AoE status removal), Starlight Heal, Glass Shield, Mind Heal, Lifewave (combos), Darksphere (combos), Soul Rune (DSC damage), Vitality rune. None are necessary, but they can be helpful. I really like lifewave and starlight heal for emergencies. Stasis rune and shadow servant can be useful in combination with Overdrive. I don't recommend shadow servant outside of Overdrive because it frequently will get removed by random effects, it doesn't combo well, and it isn't effective with DSC and tower.

• Your mystic(s) should have timeleap, time eclipse, and two optional magic spells. They should absorb mariche into sword/gloves for magic heal and tiger rampage combos. Mesarthim and Time Lord are the best mystics. Mesarthim is a great healer and Time Lord can be a good damage dealer with Time Twister or Overdrive.

At this point in the guide, I assume you're powered up in the most broken gear imaginable and nothing challenges you anymore. You thought nothing could stand up to your overdrive shenanigans. Let's fix that by challenging some uber bosses. :)

The bosses below are ordered, in my opinion, on their level of difficulty.

• You should start with Orlouge, since he is the easiest. Orlouge mostly uses magic attacks and status effects, so you should use equipment that maximizes your elemental and status resistances. Every character should have a purple eye, a harmonium earring/armor, and a Dullahan shield. Pluto armor has nice elemental resistances. Angel Brooch and Tao-Tieh pattern block additional status effects. With this equipment, his status attacks will be mostly harmless.
  
  
• Spamming DSC with 3-4 characters will end this fight very quickly. Orlouge doesn't have a huge health pool compared to some other bosses, so there's not much strategy involved if you want to brute force damage him. Be sure to have your characters topped off when all three portraits come into view, since this means big AOE damage incoming.
  
  
• Time eclipse to lower his mobility and use time leap to prevent Orlouge from taking turns. His portraits can still use abilities, but with Orlouge locked down, he is fairly harmless.

• This is the second easiest boss on the list. Similar equipment to orlouge is fine. There are a variety of status effects on this fight, so using harmonium earring, purple eyes, and angelbrooch/tao-tieh patterns are helpful. Divine ring, warrior's ring, and healer's ring are optional but helpful. There is a chance of berserk and poison status, so if you choose to exchange an angel brooch for a ring, have a way to remove them.
  
  
• Focus your damage on the Ring and ignore the minions unless Ring isn't present. They mostly inflict harmless status effects. The gimmick to this fight is that Ringlord's minions will sacrifice themselves to restore the health to everything else on the battle field. Because of this, Revolution 9 is unavoidable.
  
  
• After all minions have sacrificed themselves, the boss will gain a mobility speed up and begin using revolution 9 every turn. This does 300-400 damage to your party and inflicts some random status effects that you should be immune to.
  
  
• Use all your burst damage like tower and DSC to end the fight quickly once he starts spamming Revolution 9. A max JP tower from Rouge/blue should end the fight pretty quickly.
  
  
• Overall, this fight should be as easy as Orlouge. I killed it on my first attempt without ever being in danger of dying.

• This fight is more difficult than Orlouge/Ringlord, but still fairly easy. The boss has access to gazes and sonic attacks, so purple eyes and harmonium earrings are helpful (Noticing a pattern here?) You should have high defense gear on because he does a variety of physical moves.
  
  
• The boss' health is not that high compared to some of the others, so DSC spam can get you through it fairly easily.
  
  
• The boss uses retribution and some other higher damage aoe moves frequently, so try to keep your characters topped up between turns. Your healer will be busy.
  
  
• After a certain amount of damage, the boss changes forms. After a bit more damage, the boss casts awakening on itself. After this occurs, I recommend using tower on all characters that have access to it, as well as DSC, to burn the boss down, as he will begin using powerful physical attacks to one shot characters, as well as still using retribution. Killing him quickly here is ideal.

• Hell's Lord has a lot of AoE damage and hits very hard. I recommend using gear with high defense like power suit and dullahan shield. He has an aoe paralysis (smile) and aoe poison (illstorm). Unicorn tears can prevent poison and ailment defense items like Kris or Angel Brooch can lower your chances of paralysis.
  
  
• This boss is not very susceptible to time leap because he is resistant to status effects. Time eclipse is good in combos, and on the rare times it lowers his mobility, you can use time leap to lock him down for 3-4 turns. Basically, time leap is sometimes useful, but don't rely on it.
  
  
• To beat this boss, I highly recommend having a lot of DSC characters and trying to burn him down quickly. Blue/Rouge works as a good offhealer here with Sacrifice and Reviva. Tower is also a good idea, either as a finisher, or use it early on and switch Blue/rouge to guns/DSC. Overdrive can be helpful for a bit of burst damage, but do not rely solely on this, as the boss has too much health. Your characters should also have an alternative damage combo from DSC, because it is likely you will run out of WP.
  
  
• You should have a primary healer and an offhealer, since the damage of this boss is often too much for one character to deal with. He will often do 600+ damage to your entire party, so be prepared for that.
  
  
• When Hell's Lord is in his first form, he has a damage reduction aura. Casting a spell like phantasm or energy chain will remove it. I recommend damage dealers defend until this is dispelled.
  
  
• Dodge tremor is very useful for avoiding earthquake. I believe he also uses gale and maelstrom occasionally, so DodgeGale and Genbu Shield can also be useful.

• Amusingly, I would recommend against using T260G in this boss fight, because magnetic storm will ruin your day.
  
  
• This boss has too large of a variety of attacks to defend against everything, so you should equip to defend against his most dangerous attacks. Your characters should use Pluto Armor for faint resistance against carnage and elemental resistance. You should use harmonium earring/armor to defend against sonic attacks, sand vessel to defend against petrification, and a kris or angel brooch for additional status and elemental defense. Genbu shields for everyone to defend against maelstrom.
  
  
• Genocide Heart is predictable. Genocide Heart starts in the TV room and after a set amount of damage, he will activate carnage. Then he phase shifts to a new area. After a set amount of damage, Genocide Heart returns to the TV room and says "security level x", then he will use carnage on the next turn. This does 300-400 damage to your party, and more after V-Max. Be sure to keep everyone topped above 450 health prior to carnage. Carnage is not affected by time leap and cannot be prevented -- it is a secondary mechanic from the boss' turn.
  
  
• This boss has resistance to status reduction. He seems to have higher resistance after V-Max. Prior to V-Max, I like trying to get a time eclipse/time leap chain on him early using WP and JP efficient combos to lower his health. You don't have to bust out all the high damage, because the first phase of this fight is not that difficult. The boss has high health, so be conservative with your damage in the easy phase.
  
  
• You can see how damaged Genocide heart is by the amount of TV screens with static on them. Once all the TV screens are blank, he will activate V-Max. This is where the real fight begins.
  
  
• After V-Max Genocide Heart is now faster and does extra moves per turn and these moves deal additional damage. As far as strategy, I recommend maximizing your damage with DSC and heavy hitting combos in any of the dangerous areas (desert, ocean, snow mountains) as he has powerful aoe attacks that can easily wipe your party. Saintly halls and decaying earth are mostly status effects and less dangerous. Focus on healing for carnage when in the TV room.
  
  
• The desert is the most dangerous area, because he can use magnetic storm and heat wave. Magnetic storm is his most dangerous attack and will do over 1,000 damage to instantly kill your entire party without an appropriate amount of shock resistance. Do whatever you can to get keep him out of the desert. He also has access to time eclipse for petrification here, so I hope you equipped sand vessels.
  
  
• The Ocean is the second most dangerous area. Here, he can cast maelstrom and tower. Hope you equipped those Genbu shields. Even his thunderbolts hit really hard. Tower will instant kill anyone it hits, so beware. I've seen it do over 5,000 damage. Try to get out of here pronto.
  
  
• Snow mountains are a medium amount of danger because he has access to windblast here. It usually won't kill your party, but it can be pretty dangerous. His other attacks are not very noteworthy.
  
  
• Saintly Hall is mostly harmless if you are immune to sonic attacks. Decaying Earth is mostly harmless as he uses a lot of status effects that you should be immune to like stone gas, but poison and mess can be annoying, so be sure to bring some snake oil to remove them.
  
  
• When he returns to the TV room and all the screens are blank after V-Max, this means he is almost dead. This is the MOST DANGEROUS MOMENT in the entire fight. This is where you should use Tower, DSC, Overdrive, and basically use everything to try to end his life, because he will only use the most powerful AoE spells and carnage here. I've been wiped out at this final stage plenty of times. If you can help it, do not let him have a single turn here.
  
  
• If at any point you are lucky and have a time eclipse reduce the boss' mobility after V-Max, you should use timeleap on him to lock him down and this makes the fight dramatically easier.

• BossX is probably the toughest boss up to this point. He has the largest health pool of all bosses, which I've heard is around 300K. He has the very dangerous hyper and charm gazes, so equip those purple eyes. He uses poison, but it seems to be infrequent, so unicorn tears are probably unnecessary. He often uses Lord Cannon which hits up to 5 Times (Wonder Bangle doesn't work on this). He uses flash, so powered suits with blind immunity are helpful. As usual, 1-2 Dullahan shields for everyone for resistances. He doesn't seem to have any sonic or mind attacks, so the last two slots can be filled with general resistance/defense charms like Kris, Angel Brooch, Windshell, etc.
  
  
• Time leap is useless on this fight since he nearly always has priority to move first. Lowering his mobility does not change this.
  
  
• This is a boss that you probably want DSC and tower on four characters. It is probably doable with 2-3 characters with DSC & tower, but having four makes the burn phase significantly easier. Remember that tower damage is tied to JP, so you want your JP to be over 125 for all characters using it.
  
  
• This boss has two phases, but he does not visibly transition like other bosses. I believe the transition occurs somewhere between the 50%-75% mark. Once he enters phase two, he doubles his attacks per turn. Lord Cannon will now hit up to 10 times, he will use multiple gazes, he has some other aoe attacks, and he will begin using Judgment X. Judgment X is a powerful attack that hits the entire party for 400-500+ damage, and also causes the sleep status effect (not a huge problem since it wears off quickly). It is possible for him to use this Judgment X multiple turns in a row-- pray he doesn't. Given that he also typically moves before your characters due to his high mobility, you want to immediately heal any character that is below 800 health.
  
  
• Similar to Genocide Heart, take it slow in phase one. He's not very dangerous here and you can usually heal his damage up fairly easy. Use cheap boundshot combos with time eclipse, life wave, dark sphere, etc. to save your resources. Before phase two, I thought this might be the easiest boss on the list. It's fine to take your time here. You want to save your DSC and Towers for phase two, because it is a damage race at this point. His damage simply isn't healable once he starts using Judgment X, because your healer will quickly run out of LP for life rain.
  
  
• Due to his high health pool, you will run out of WP if your entire strategy is to DSC him to death. Use cheap combos in phase one, unleash DSC and tower in phase two.
  
  
• Alkaiser with final crusade for extra healing is also a viable character if you choose to train him up for this fight. I would highly recommend it if this fight gives you a lot of trouble.

• This boss took me probably the most attempts. He has access to sonic attacks, so sonic immunity is a must. His gun shots don't seem to be avoidable with wonder bangle, so I wouldn't waste time with it. Other than that, try to maximize your physical defenses and max out your stats like vitality if possible. He has access to tremor, so dodge tremor can be helpful.
  
  
• I recommend using a gunner strategy with bounding shot/trick shot on this boss. This is because he seems to take reduced damage from DSC. I never had my DSCs hit him for more than 10k, so it seemed inefficient when bounding shot would hit for 5k (or 7k with light rifles). And given that he has five health bars, you will run out of WP pretty quickly using DSC.
  
  
• The first three phases of the fight are fairly easy. Simply top off his damage each round and use efficient combos to take his health down. In the second phase and after, he will use enflame, which is a chainsaw attack that can instant kill. It's blockable.
  
  
• Time leap works in phase one of this boss pretty well. This can help you get an easy transition to phase two. After phase two, the boss' mobility increases and it's no longer worth using.
  
  
• Phase four gets difficult. He can now use enflame multiple times per turn. He also gains access to the beam cannon, which is usually only present on phase five in the non-super version of this boss fight. The beam cannon will usually one shot the character it hits, so you need multiple characters with healing spells in case the healer gets hit. He also hits the entire party with a gun shot attack frequently here, as well as spamming various aoe missile attacks. You can use DSC here if you want to, or just continue with bounding shot combos. Your healer will have a full-time job keeping everyone alive and you should have other characters with backpack or starlight heal to heal the healer.
  
  
• Phase five is the most difficult part of the fight. He begins unleashing massive amounts of damage every turn. Once again, this is the burn phase part of the fight, because it will be very difficult to keep up with his damage here. A full round of towers, with one from a max JP rouge, can end this fight in a turn or two.

Spoilers ahead. You've been warned (again).

• There is an additional secret boss in the dev room after beating Fuse's scenario. It can only be challenged after closing all of Fuse's case files. This boss should only be challenged when your stats are very close to being maxed out. 900 health is a minimum. He should also be challenged after beating either Red, Blue, or Riki's case file for the benefits they provide. Red has access to Final Crusade, which is a very good healing ability life life rain. Blue has access to sacrifice, which is also like life rain, and also all magic, making him a powerful character in this fight. Finally, Riki has access to the divine ring, which restores JP/WP, which is useful for this fight as the boss has a large health pool.
  
  
• This boss is called Ninja. As far as I know, no one has beaten him yet, but what we know right now is there are at least three phases to this fight. He is resistant to all damage that isn't a combo. DSC is not useful on this boss. Overdrive is only useful as a support skill for casting buffs and heals, because Ninja cannot be effectively damaged in the absence of combos.
  
  
• Ninja begins the fight by attacking two characters with a petals attack that hits for ~1800. It can be survived by defending with all characters on turn one. After this, you should heal your characters and try to time eclipse him to lower his mobility stat. In phase one, he is vulnerable to time leap, so keep him locked down and put some buffs on your characters. The time eclipse debuff needs to be refreshed every 3-4 turns.
  
  
• Ninja can only be effectively damaged with combo effects. There is a hidden mechanic in the game where all moves after the first in a combo ignore armor, thus making it possible to damage Ninja through his absurdly high defenses. At this point, I feel a gunner strategy with bounding shot is ideal. Bounding shot easily combos with itself and has a chance to ignore armor. I would advise to have dual light rifles on all your gunners to maximize damage output.
  
  
• Once you've done enough damage, he will enter phase two. He often begins this phase with retribution and heavy aoe, so I would recommend defending on the first round. Many of his moves can be dodged with dodge skills - dodge spore, dodge tremor, dodge gale, dodge net are all relevant if you have them.
  
  
• In phase two, Ninja is immune to timeleap, but he can still be slowed with time eclipse. It is important to slow him down so that you can act before he does and heal/combo properly.
  
  
• Farming life candy may help keep your life rain users alive longer.
  
  
• I've only heard this from others and cannot confirm, but: eventually, after doing enough damage, there is a third phase. If you do not kill him quickly enough here, he will run away.