Game:Vexen

Vexen is fought as a boss in Kingdom Hearts: Chain of Memories, and can also be fought twice in Kingdom Hearts II: Final Mix+. He battles Sora several times in Chain of Memories, as well as Riku in Reverse/Rebirth. In Final Mix+, you may battle his Absent Silhouette in Agrabah, or have a data rematch in the Garden of Assemblage.

Kingdom Hearts: Chain of Memories
An easy way to defeat Vexen is by using sleights in quick succession. Blitz and Sonic Blade are powerful and do large amounts of damage. The Jafar card is very good to use in this fight, as it will prevent Vexen from breaking your attack cards. Make sure you also leave three or four zero cards at the front of your deck in order to break his sleights, Freeze and Ice Needles. Put some Cure cards at the back of your deck as well to be used in combination.

As for avoiding Vexen, keep moving. When Vexen says, "I'll freeze you!," start dodge rolling so he doesn't catch you in his ice block. When he slams into the ground, keep running to avoid the ice spikes that will follow you around the battlefield.

This battle can be very difficult, so just keep trying. The Jafar card can save you, however, as it will prevent Vexen from his annoying habit of breaking your sleights with zero cards.

Kingdom Hearts II: Final Mix+
Vexen appears as an Absent Silhouette and a Data Battle.

In this battle, Vexen wields his shield in front of him, preventing you from damaging him until you deplete the shield's HP bar. Vexen often throws spinning shields at you, which you can get rid of by guarding or reflecting. He will also conjure up pillars of ice, but this is easily avoided by dodge rolling. When you see snowflakes reflecting across the screen, use Reflect, so you don't become frozen and have to break out.

Vexen also has a data circle that follows Sora around; do your best to avoid it. When it gets to one, Vexen summons an Anti-Form Sora, and can be troublesome. It then can go to 2, 3, 4, and 5, each time making a more powerful Anti-Form. If your magic is high, use Reflect, and you will be able to kill it quickly.

Vexen's weakness is Fire. After you get his shield down, go into Final Form or Wisdom Form and attack repeatedly with Fire. It would be useful to use the Keyblade, Bond of Flame, to deal greater damage. When he summons his shield again, rinse and repeat.

Attacks from Kingdom Hearts (Re:)Chain of Memories
Attack card: Vexen comes close, attacks with his shield and juts out an ice pillar.

Magic Card: Vexen summons an ice shard to home in on Sora similar to Sora's Sleight Homing Blizzara.

Sleights
Freeze: Vexen focuses his power on Sora/Riku encasing him in ice and coming in close to attack dealing additional damage. Only Sora can learn this sleight.

Ice Needles: Vexen channels his power into the grounds creating icicles that shoot up from the ground and attack Sora/Riku.

Slide Break (Against Sora Only): Vexen focuses his power into his shield turning it into a long Ice Blade. He then comes at Sora to attack him with said blade and then slams it in the ground thus shattering it. He uses this attack only against Sora.

Diamond Dust (Against Riku Only): Vexen creates a swirling blizzard around the area damaging Riku. He uses this attack only against Riku.

Battle Quotes
"Taste this!" "Here you go!" "No good!" "I shall freeze you!" "I've had enough of this!" "Away you go!" "Shatter!" "You're pushing it!" "You imbecile!" "You are just an experiment!" "You're too much trouble!" "How do you like this?" "Now, feel the piercing chill!" "Come to me, Ice Blade!" "Hmph! Gloat while you still can!" "You have no fate..."