[Snake]

This could use a buff. I mean, in games like Skyrim a perfect Sneak Attack does what? 300%-600% damage? But I don't want to get extreme. What I say is:
Sneak Attack - Damage dealt while you have Sneak active is increased by Rank x 25% (up to rank 4, like Buster Cannon). (making a total of 100%, a 'critical strike' for having sneak.)

(For the salty complain-y Lupines out there, 100% = normal attack power, what I want is 100% + 100% from 100% + 10%, mostly because that's worth a what? Ogata's Waraji? lol.)

Why?
1- It will give Spellthieves motivation to get sneak, both thematically and to use this wonderful buffed buff if people don't throw ounces of salt on me for suggesting this.

2- You only have sneak once, and it poofs forever in the battle when you do any sort of damage. Like Pocket Sand.

3- It will put the Spellthief in a situation of: "Do I first buff for the NSEW winds to grant I won't get pwned on the first two rounds? Or do I try to rush the enemy now for the 2x damage and risk being pwned?"

4- Great Reckoning 2, Talent Revamp. Sneak active is still lackluster. (A free skip for the monsters and chabooski, that's all sneak does.)

5- Rogues don't have a good, solid autohits to abuse it. And most of them would need atleast Eastern Wind to get their HIT buff in order to land a proper basic attack.

6- I've contemplated making it 'Physical' only, but Spellthieves use magic.

7- Damage Reduction in % won't make this look so special anyway.

[Neus]

This would make Umbrals OP.

[Snake]

Oops, I did a nice overlook. Didn't knew Fade Out adds Sneaking buff to the Umbral.

Anyway, it costs 3M to use Fade Out, so it would be as fair as a gunner using Charged Shot followed by a basic hit. But since Umbrals are a thing, I can't ask for higher numbers.

Can it be increased to 25%? Doesn't seem to be an OP damage buff for me. Plus, Umbrals are not really a common race around the world (read: players), like Vampires, Kaelensian or Mechanations.
Having 'Sneak Attack' a special gimmick for Umbrals would be as fair as Leporidae's 'danger sense' passive being used with Kensei's Sheath Sword/Quick Draw. Or Corbie/Hyattr's Gain Air being used with Winged Serpent.

[Ranylyn]

This would make Umbrals OP.

Thank you, Dev. For beating me to it.

[Snake]

Oh well, R.I.P Assassin's Creed dreams.