Kingdom Hearts: Final Mix > Hidden Boss
There were several new bosses added to Final Mix that weren’t included in the original Japanese release of Kingdom Hearts. Most of those bosses were included in the international release however, so only one new boss in Final Mix is actually new to international gamers: the Unknown.
HP: 1500 | EXP: 12,000
The Unknown is a really hard adversary who doesn’t pull any punches. You’ll need Curaga, lots of MP, lots of Elixirs, Second Chance, Leaf Bracer, and the Tinkerbell summon – along with the most powerful weapons you can get on all three of your characters.
When you’re prepared, head toward the glowing purple orb in the “Castle Chapel”. Donald and Goofy(no Beast) should be in your party.
The Unknown’s assaults are relentless and leave very few opportunities to land some hits without being hit yourself. The only real strategy during this initial part is to continuously attack him no matter how many times he blocks you or hits you, pulling out occasionally to heal yourself with Curaga. Donald is usually pretty good at healing you during the first few minutes of the fight, but once his MP runs out, you’ll be on your own for healing. This is a good time to summon Tinkerbell, who will constantly heal you over quite a long period of time. Don’t rely too heavily on Tinkerbell to save you though, as the Unknown’s attacks are often too quick for Tinkerbell to keep up with.
One particular attack to really watch out for can be recognized when the Unknown grabs Sora in some kind of energy beam. This attack takes your Menu controls and replaces them with new options. One option is different from all of the rest, and you need to hit that Command as quick as possible to reclaim your normal Menu Commands. If you hit anything but the different Command, the beam encasing Sora will deal some pretty nasty damage.
Another attack to keep in check is the Unknown’s most powerful assault. He’ll encase himself in a giant energy orb and fire gigantic lasers that slowly move all over the room. He is completely untouchable during this attack, so focus primarily on not getting hit by the lasers. Since the Unknown isn’t attack nearly as relentlessly as he usually does at this point, this might be a good time to take an Elixir if you need one.
Basically, keep hammering him and healing yourself when needed and he’ll eventually fall. Victory in this fight earns you the EXP Chain Accessory and Ansem Report 12.