After beating the secret room, swim up ahead following the trail of Red Orbs and begin hopping up the platforms. You’ll see a freaky eye on the wall just staring at you while it will shoot out fireballs. When it does, slash it before it hits you to deflect it back. This will destroy the wall and flood the room. There’s now some Erupt Gels so get rid of them if you want or they’ll become really pesky. Behind the wall is another piece of the a blue orb. Now keep swimming up and out of the hole and then down the other one down the path. Pass through the hole between the two pillars with red orbs. After inspecting the blue light above, slash the blue spheres around much like the puzzle in Dante’s mission which will reveal pillar stairs that will lead to another room with some Gbusmsira. Defeat them first before attempting to solve the next puzzle.
In the room ahead lies the Quick heart behind a seal. In order to access it, you need to have all 3 of the blue orbs destroyed. The catch however, is that they respawn quickly and re-activate the seal. The trick here is to try and weaken all 3 orbs as evenly as possible and destroy them in rapid succession. This should give you enough time to grab the heart before they respawn.
Continue on where you will experience some déjà vu.
This boss is very similar to Tartarussian from Mission 2 so use the same tactics. In this case, you’re better off using your melee attacks but as always just be sure to dodge his close combat attacks. Throughout the match it will summon lasers that will move in a vertical, horizontal, or full grid across the screen similar to Griffon. Get the Arcana and head into the next mission.