PrinceWatercress plays Majuu Ou (King of Demons) - Part 3 of 3

Here we are: the final battle!

Stage 7

The ultimate form has a fireball for a normal attack and four columns of fire that shoot forward from the ground for the charge attack. The teleport is a slide forward. 

With each room you enter, you'll have to fight palette swaps of boss enemies that you've faced in the past. In order, you'll face the spider from Stage 1, the worm enemy from Stage 2, the scythe arm enemy from Stage 4, and two new enemies we haven't faced before. If you need to replenish health, there are fairies you can snack on between rooms.

The first new enemy is a laser eyeball from Stage 4 with a snake-like body. Use the charge shot to get rid of all the worms it shoots out as well as to damage the boss, and keep your distance. You should be good.

The second new enemy is a face. When you enter the room, go all the way to the right. This is the resurrected King of Demons. Iria will pop out of the forehead cavity before the boss finally fights you. The face then transforms. From the far right, keep double jumping while shooting fireballs at the eyes. When you see the blue lightning orbs, stop jumping, then double jump when the orb is about to hit the ground to avoid being shocked. When the mouth opens, the King of Demons will spit fire. If you're all the way to the far side of the screen and you're on the ground, the fire won't hit you. As you attack, you'll shoot down the horns and the eyes, and when that happens, the head will try to crush you. Stay to the far right and use your charge shot to get that last bit of damage in. When this boss dies, go all the way to the left.

With the King of Demons gone, Iria will pop out of the King's forehead, now in a demonic form. Unfortunately, she now turns on you. She has a double jump attack where she drops down and slightly forward to kick at you, and she also has an attack where she dashes at you. Move away to avoid the former; double jump to avoid the latter. If she shoots a red light out of her hands, be ready to keep your distance and be in mid-air to avoid the projectiles. In-between attacks, she will hop at you. Use this opportunity to hit her with normal attacks.

If you die when you reach the King of Demons, you'll start at the King of Demons; otherwise, you'll have to repeat the boss rush again.

When you beat Iria, you'll get one of two endings. If you didn't get the ultimate form, Abel will turn back into a human and try to take on the final boss again, but Iria dies, sadly. In the good ending, Iria finally snaps out of it, then Abel becomes the new King of Demons. You've beaten the game and got the good ending! Congratulations!