its possible create new masteries ?

[Jair]

i want to add this new skill in small charm, but how to create a new mastery ?

Elemental Mastery
Magic Mastery
Poison Mastery
Physical Damage Mastery

[gogodanny]

How to make a new mastery: Clone an existing mastery and change dmg-type.

[Ogodei]

You can also create a dummy passive and let the skills synergize with it (synergy fields in skills.txt). AFAIK that's the simplest way to do a magic mastery skill for spells