How can i add a Drain skill that takes away the enemies health and replenishes the users?
How can i make a certain weapon Melee attack then shoot a bullet?
How can i make moves like, Armor Break, Power Break or something like that?
How do i change the battle music?

Blizzard's Tons of Add Ons:

http://forum.chaos-project.com/index.php?topic=105.0

There is a script in there that absorbs HP/SP. I already answered your gunblade question. Can you be more specific on what Power/Armor Break does? If it lowers the enemy's DEF then it can be easily done through the Database and States. You can change the battle music through the Database if you look harder.