Zero's forms
Energy Form (Yellow)

Enemies drop more Energen Caps. and Crystal Caps.
Grab 25 Life Capsules to unlock.
Power: ***, Defense: **, Speed: *
X Form (Dark Blue)

Buster becomes more powerful while shooting a charged shot; you can now fire more quickly.
Kill 50 enemies with Buster Gun to unlock.
Power: ***, Defense: **, Speed: ***
Power Form (Purple)

Always biggest saber edge.
Pull anything 30 times with the Chain Rod (even slightly) to unlock.
Power: ****, Defense: **, Speed: *
Defense Form (Light Green)

Damage taken is halved.
Kill 20 enemies with charged Boomerang Shield to unlock.
Power: *, Defense: ****, Speed: **
Active Form (Orange)

Z-Saber is "upgraded". You can now do roll saber attacks, and more damage while jumping.
Kill 20 enemies with Dash Slice attack to unlock.
Power: **, Defense: **, Speed: ****
Erase Form (Magenta)

Z-Saber and Shield can destroy enemy's bullets.
Get 30 ricochets with Boomerang Shield to unlock.
Power: **, Defense: ***, Speed: **
Rise Form (Light Blue)

Up-slash in 3-hit-combo.
Kill 10 enemies with the Z-Saber to unlock
Power: **, Defense: **, Speed: ***
Proto Form (Dark Green)

All weapons at level 1, but major power.
Complete the game to unlock
Power: ****, Defense: *, Speed: **
Ultimate Form (Red)

Allows special key commands for charged weapon
Obtain it by using every Cyber Elf.
Power: ***, Defense: ***, Speed: ***