To improve the object must have: God Magic Crystal
Which you can get from tasks, quests, events, or after killing "Predator".
god magic crystal is added, depending on luck of from 1% to 2%
hp- life, mp- mana, ML- magic level, skills - club, axe, sword, dist, shield
every item you can attach 7 god magic crystal.
Remember, you can not use it on:
arrow gp's etc items, which do not have defense/attack.