Alright, so the location of the fight is simple enough, head to the top of the volcano (from the entrance of the volcano, head left, defeat the 2 moles, double jump through the roof on the newly raised ground, then head to the right and you'll eventually find yourself there). You'll notice a new portal to the right of the apple orchard.
Mercifully, there is also a save point nearby.
SECRET(?) BOSS: Enit
Welcome to the hardest fight this game has come out with so far and (imo) a refreshing challenge and change from the usual fare.
She attacks in 3 predictable phases:
Rushdown phase: She comes at you Metal Gear Solid style with a 3 part attack: 2 punches and a finishing kick that gives her a deceptive amount of reach.
At the start of the fight she always executes this combo twice but later on she will do it 1 to 3 times, seeming to depend on if you take the hits and if she is enraged. Each hit does a small amount of damage but they can combo together to add up to a decent chunk of your health if you take the full combo. Best way to avoid this is jump over her and away, preferably with the double jump ability for added safety.
After this attack she will stand still for a second, jump into the air and begin channeling magic energy for...
Dark Magic Pillar phase: After a short time charging energy (during which she is completely invincible) she fires a dark magic ball that travels at moderate pace to your current location. After hitting the ground it explodes upwards into a persisting pillar of black magical death, sending a shockwave along the ground in both directions.
Failure to avoid this attack will result in you getting blasted upwards and then landing painfully on the ground for a staggering amount of damage (Over half your maximum hp!)
Luckily there are a few ways to avoid this.
A) Equip the kappa dash and dash under her once she let the ball loose. Despite being right next to her it still takes time for the ball to hit the ground, easily enough time to execute the dash and avoid the pillar. Then just jump over the shockwave. I highly recommend this method because it puts you in a great position for the next phase.
B) Equip the first ability (the one that increases your overall speed) and stand somewhat close to her. Once she lets the ball loose, just run away. You'll outrun the explosion and have enough time to jump over the shockwave. This is probably the safer way to deal with this attack.
Last important aspect of this phase is that after the pillar eventually disappears, it will leave behind 2 dark orbs at the top of the screen. These will damage you if you touch them and stick around until she uses another dark magic ball. The only time you really need to worry about hitting them is if you are using rabbit double jump.
After she fires the attack, she will transition into the last phase...
Seduction phase: After around a second of charge time, she sends out hearts in 3 directions: upward, left and right. Getting hit by these will cause you to sprint towards her and recieve a blowjob which you will not be able to escape from, costing you about 40% of your hp (you can technically fight the trance before the blowjob but in my experience it's impossible to mash out of it before you reach her no matter the distance).
The hearts are deceptively slow so make sure to properly judge the timing before jumping. After you dodge them will be your chance to counter attack! Equip the Cat Scratch and attack her as many times as you can. If you used method A to dodge the dark magic pillar you'll be right next to her and might possibly get enough attacks in to send her to her next "form". If you used method B you'll have to wait for the pillar to disappear which will cost you a few hits on her.
Either way, after she stands back up she'll begin attacking again starting from the first phase after a short delay so be prepared to avoid her attacks.
After dealing enough damage, she will visibly recoil. This signals the start of what I call "enraged" form.
Enraged Form: During this time, most of her attacks are augmented
Rushdown phase: She moves and attacks faster and hits harder. She now chains this attack up to 3 times in a row.
Dark Magic Pillar phase: The ball travels faster and pillar is close to twice as wide once it erupts. Timing to avoid it becomes somewhat strict.
Seduction phase: No changes that ive noticed (Requires more testing)
Keep attacking her once she's vulnerable after seduction phase and you will eventually triumph. Good luck!