The Kingdom Hearts series contains many bosses, and even the spin-off titles get their fair share of them. Birth By Sleep, the PSP prequel to the first game, tends to have more of a mixed bag in spite of its otherwise excellent combat system, but there are still plenty of bosses which put up an entertaining fight.

These aren't necessarily the hardest bosses in the game, although a few will certainly take many attempts before you can defeat them. What they do have, regardless of difficulty, is a satisfying combination of mechanics, spectacle, and balance, and you know you're in for a good time when you start fighting them.

10 Zack (Terra)

Zack and Terra facing each other with a smile

Long before Sora meets Cloud, the trio of BBS encounter Zack from Final Fantasy 7: Crisis Core. Terra's fight in particular starts off as a friendly scrap, and Zack goes down pretty easily. However, it becomes much tougher when Hades manipulates the darkness in Zack to fully control him.

Here, Zack is far more relentless, and he can easily drain your health if you underestimate him. Keep an eye out for his rapid attacks, and make sure to exploit the moments where he tries to fight off Hades' control.

9 Captain Hook (Ventus)

Screenshot of Ventus near the camera and Hook further away as they prepare to fight

Captain Hook is a recurring villain within the Kingdom Hearts series, and this may be the best fight against him. He's a fierce sword combatant, easily able to slice through your health in a matter of seconds if you're not blocking or dodging.

Luckily, you have the assistance of the crocodile who is lurking nearby, eagerly waiting to take a bite out of Hook if you're able to knock him into the water. This distracts Hook enough for you to get in a few free hits.

8 Vanitas: Badlands (Ventus And Mickey)

Vanitas and Ventus fight in the Badlands

Vanitas is the evil opposite half of Ventus, and also proves himself to be a fierce combatant at multiple points throughout BBS. In fact, this early encounter within Ventus' storyline is an excellent demonstration of his power.

Even though you have the assistance of Mickey Mouse, Vanitas puts up a strong fight (and yet is still holding back). Make sure to take full advantage of your strong shotlock commands, and if Mickey is keeping Vanitas busy, use those brief seconds to heal or set up your own attack.

7 Trinity Armor (Everyone)

Aqua dodging the Trinity Armors laser attack

This is the only boss fight in the game where Terra, Aqua and Ventus are all fighting the same opponent together, which makes the overall moment feel much more special. Regardless of you're playing as, the other two will be fighting by your side, and they're no less competent than you are.

It's technically a multi-stage fight too, since you need to defeat all three sections to fully succeed. Even so, it doesn't feel drawn out, nor does it feel like things are over too quickly.

6 χ-blade Vanitas (Ventus)

Image of the Ventus and Vanitas Station of Awakening artwork

The climax of Ventus' bouts against Vanitas actually takes place within Ventus' own heart, as he tries to wrest control of his body from his evil twin's influence. This time, Vanitas is wielding the χ-blade (literally pronounced "key-blade") and has new dark powers.

Eventually, he breaks the platform you're both standing on and you both end up fighting in zero gravity. You can't actually defeat Vanitas until you strike him with the final command of Last Word, the combo finisher. (It's possible to miss it, so be careful.)

5 Master Eraqus (Terra)

Master Eraqus holds out his keyblade as he prepares to fight

This is one of the sadder fights in BBS, as Terra has to fight his own mentor to defend Ventus. Eraqus harbors a deep hatred for the darkness whilst Terra has been trying to bury his own within himself, but it's this moment which causes that darkness to fully manifest itself.

As can be expected with fighting someone who holds the title of "master," Eraqus has several powerful moves at his disposal. He can easily parry and interrupt your attacks if you get too greedy, even your new dark powers.

4 Terra-Xehanort (Aqua)

Aqua fighting Terra-Xehanort in his second phase

This fight takes place during the Final Episode of BBS, and is subsequently difficult as a result. The first phase is similar to the final fight of Terra's story, but in the second phase, Terra-Xehanort is assisted by a Heartless who sends out its own attacks and can even grab Aqua if you're not careful.

It's a fairly heart-wrenching encounter because Aqua's trying to free her friend from Xehanort's control, and even dooms herself to the darkness in order to save Terra. And sadly, it ends up being for naught.

Aqua shooting a Triple Blizzaga at Dark Hide

This boss appears during the secret episode with Aqua, which was added for the PS3 and PS4 remasters of BBS. It's one of the few occasions where you actually fight a Heartless in BBS instead of an Unversed, although Aqua only knows it as a "creature of darkness."

Dark Hide hits very hard and moves incredibly quickly despite its size, which is made harder in the opening phase because you can't fully see it. Also, it only gets faster in subsequent phases, so pack your strongest abilities and don't get greedy.

2 Armor Of The Master (Everyone)

Eraqus' keyblade armor pointing a keyblade towards the screen

Much like Aqua, Ventus, and Terra, Master Eraqus has his own set of armor to protect him from the darkness between worlds, and you can fight an animated set of it in the Mirage Arena. Much like Eraqus himself, this armor is no pushover.

The armor is very fast and hits just as hard, and it doesn't have many openings either. Therefore, equip some attack commands which are tricky for it to block and always have multiple healing options, such as Curaga or hi-potions.

1 No Heart (Everyone)

No Heart sitting on Eraqus' throne

The secret bosses in BBS can be a bit of a mixed bag, as anyone who's fought Mysterious Figure will be able to attest to. Thankfully, No Heart is one of the better secret bosses, although he's certainly not easy.

This fight is split into two phases, but the real insult comes from the fact that he doesn't even bother to stand up for the first phase. Rather, he sends a projection of himself to fight you, and only after you've defeated it will he face you himself.

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