Based on your alignment (holy/evil) you have a set of spells you can buy for battle. Each spell would cost some form of currency. Once you've accumulated a few spells you can then set those spells as active up to around 3 different spell types.
In battle those spells will then have a % chance to be casted based on either a new magical stat or the way the game works now.
When your spell is casted it then will remove a charge from that spell. So say you had 5 "increase attack" spells, cast one then there are only 4 left.
An example of how this works can be seen here: http://skylnk.co/vKtFnr
Hit enter to run the battle, you'll see you cast different types of spells and each time it's cast the game removes the correct amount from your inventory.
Spells can also be broken down into types: BUFF, DMG, SUPPORT to name a few.
BUFF: Spells that benefit the player, "Increase attack", "Increase defence", "Increase Evasion"
DMG: Spells that deals direct damage to the enemy.
SUPPORT: Spells that will Heal or remove debuffs the player might have.
Many more ideas can be thought of but these are just a quick few.
Now with this system it adds a huge amount of potential for more varied battles.
Lol (1039)'s addition. (slightly modified)
Allow users to cast purchased spells on another user. Any user you cast the spell on then receives a cool down time for when you can cast on them again.
Spells can be similar to the ones previously mentioned.
