Ventus: Max HP+5
You will face off against the Mimic Master, an Unversed only accessible in the Mirage Arena. He utilizes a large book, with which he can hit you with for shockwave damage, or use to create a shield of pages around himself. He can cloak himself in fire, and shoot beams of light and darkness.
However, most annoying of all his abilities is his power to morph himself into an exact copy of your player, but this copy uses dark attacks as well as your own. Despite the Mimic Master's wide array of attacks, he is not a hard boss. He leaves many open spots, and his attacks, on the whole, are rather weak.
Use Shotlock commands such as Absolute Zero and Photon Charge to get in as many hits as you can before switching to strong magic commands or long range (and fast) physical commands like Sonic Blade or Zantetsuken. It may be a good idea to get hit by his fire attack, because unlike the Iron Imprisoners, it does minimal damage, and will stop soon after you take damage, and so you can speed up the battle.
The most difficult part comes later on when he creates dozens of copies of your character. The best way to handle this is just Shotlock and try not to get blinded by their array of dark commands. This battle is not a hard one, but make sure you come prepared with a Curaga and advanced magic commands.
A "dead ringer" is someone or something that very closely resembles another.