Default, this one comes free

long quest to unlock this one, you can bypass all of it. go to the Magnetic Fields and play until you hit a safe point. on the top left corner is a 4 digit code lock, use the 4 color coded pillar buttons to put in 7293 and BAM you just saved a good 30 40 minutes of running around.

unlocked the slasher well playing the cores from left to right and i died on my 3rd core run

to unlock this one you need to beat one core run without using a single MAIN attack, you can still use Effects. i used the slasher and went full deflect. Hollow Hive is your best bet

no idea how i unlocked this guy, but it sure wasn't how all the guide said to

Beat the full game. you need to clear 3 runs of your choosing and beat both final bosses
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and remember kids. if you see my steam guides anywhere off steam, those ♥♥♥♥♥♥♥ stole it!