Ok, I got the solution! 
Shadow Mastery:
- All wdef is ignored with every skill (unlocked @ lvl 1~10 of the skill)
- Allows you to use pots in Dark Sight (unlocked @ lvl 11~20 of the skill)
- Allows you to recast all buffs in Dark Sight (unlocked @ lvl 21~30 of the skill)
- All skills have double MP usage at max lvl
- Boost all skills percentage wise by 150% at max lvl:
Sblow - 480% > 720%
Assaulter - 450% > 675%
BoT - 210% > 315%
Bstep - 1000% > 1500%
Assassinate - 2650% > 3975%
Shadow Mastery replaces Ninja Ambush completely...
So... Nexon, what are you waiting for?

Shadow Mastery:
- All wdef is ignored with every skill (unlocked @ lvl 1~10 of the skill)
- Allows you to use pots in Dark Sight (unlocked @ lvl 11~20 of the skill)
- Allows you to recast all buffs in Dark Sight (unlocked @ lvl 21~30 of the skill)
- All skills have double MP usage at max lvl
- Boost all skills percentage wise by 150% at max lvl:
Sblow - 480% > 720%
Assaulter - 450% > 675%
BoT - 210% > 315%
Bstep - 1000% > 1500%
Assassinate - 2650% > 3975%
Shadow Mastery replaces Ninja Ambush completely...
So... Nexon, what are you waiting for?

