In Co-op you can ally with up to 5 other members and take on bosses. Your weapons and equipment that you had equipped from the file you loaded for Co-Op will retain their stats and upgrades from the loaded file.
The first time you clear a boss you will obtain a weapon, the second, and everytime after that, the materials needed to upgrade the weapon. You can rarely receive a Rose or Coral after beating a boss several times. Rose and Coral can also be earned in Deathmatch. The bosses you fight are: Kraken, Last Cocoon, Nebirous, Muruk, and Sentinel Beasts: Atar and Mitra.
Notable differences in strategy:
Kraken (Reward: Claw Sword)
- No longer takes extra damage from Vertical Slash
- One Heal Bomb spawns on the fallen rock blocks near where your party starts. Another Heal Bomb spawns on the steps behind the party.
- Still absorbs Ice element
- Summons Sea Reptids. Sea Reptids drop Magic Essence, Power Essence, Accelerate etc. when defeated.
Last Cocoon (Reward: Trident)
- Guard Break to deal decent damage (requires Yurick and one melee diffuser) when in upright form.
- After a while, transforms into the bull version. Defense lowers but moves fast.
- Bull version will run in a straight line toward one player. Throw a Daze Bomb right in front of the path to try and daze Last Cocoon while in Bull form. Daze Bombs won't work when Last Cocoon is in upright form.
- Last Cocoon summons Gurak enemies each time after transforming back to upright form. Notably, a Reptid Witch that will cast a red damage circle and the melee Reptids can inflict Poison. Reptids can drop Magic Essence, Power Essence, Acclerate when defeated.
Nebirious (Reward: Eclipse)
- Co-Op version requires 3 Silver Arrows to stun.
- Heal Bombs periodically spawn in two rooms.
- Silver Arrows will almost always drop from the Skeleton archers (inflict Sticky or Paralyze) that constantly spawn
Muruk (Reward: Spirale)
- Magic Essence, Power Essence, Accelerate etc. will periodically spawn in the corners of the map.
- One Heal Bomb spawns (and periodically respawns) to the right of where your party starts.
- When Muruk turns into a ball, he will roll around the battlefield causing lots of damage. Don't try to damage him during this stage and just guard. Standing close to a pillar not on the outer rim where Muruk seems to roll the most in seems like a good place to stand.
- When Muruk loses 3/4 of his health, he will start changing elements, indicated by changing his color to blue or red. He will start to change elements more frequently as he loses more HP. When he is about to change, he will start by rolling around the battlefield first.
- While he is spinning, try to retreat to one of the corners if you want to avoid the large fire / ice magic splash and bad effect.
- Muruk's fire / ice magic drops a big magic circle. You must diffuse this or your weapons will be enchanted to deal the damage Muruk currently absorbs.
- Muruk's fire magic inflicts Guard Break if you're hit. Ice magic inflicts Slip if you're hit.
- When Muruk is red, he absorbs Fire. When he is blue, he absorbs Ice.
Atar and Mitra (Reward: Dragoon)
- When Atar is reduced to half health, Mitra will enter and fight your party too.
- Magic Essence, Power Essence, Accelerate will periodically appear between pillars on the battlefield.
- Heal Bombs will appear around the battlefield.