I have to agree with uv23... This is a list of feats that the character could have otherwise taken, and a significant reduction in sneak attack ability. The player who wants these benefits would get the same number of feats (and some other bonuses) by taking fighter levels intermitantly.
Sudden Strike: Not quite as good as Improved Initiative, which could be taken with a fighter bonus feat.
Improved two weapon fighting: It's a feat, but it's a significantly powerful feat, awarded without the all requirements being taken... I'm going to presume, however, that anyone working their way into this class will take Two Weapon fighting, since Ambidexterity is sort of worthless otherwise, meaning that this feat could just be gained by taking fighter levels.
Deadly Strike: This is sneak attack. Six levels worth. I'll come back to this.
Greater Weapon Focus: It's not a feat that can be taken, but taking levels of fighter would give a BAB bonus that would outweigh this bonus in usefulness.
Ghost in the Wind: A lovely name for a bunch of skill bonuses. This is the only thing that can't be duplicated with multiclassing.
Critical Strike: Another feat that can be gained by multiclassing.
Improved Evasion: Something that would be gained with a few more levels of Rogue.
So: You have to be a fifth level rogue to gain entrance to this class. Presuming you want this class, you're not giving anything up to get in (You're going to take ambidexterity, if you want to two weapon fight), except Weapon Focus Shortsword (Rogues already have short sword proficiency, so that's a non-issue. Here are two 15th level characters (I'm presuming your class has a rogue BAB):
Rogue 5/Shadowthorne 10 (BAB +10)
Rogue 11/Fighter 4 (BAB +12)
The second one can spend his bonus feats on Improved Initiative, Improved Critical(Shortsword) and Improved Two Weapon Fighting. He gets a BAB two points better (better than any benefit he would have gotten from greater weapon focus), better hit points, a slightly better will save, a better fort save (but a worse reflex save), the same sneak attack damage and all martial weapon proficiencies. It's arguable that the Shadowthorne will have better skills (especially hiding and moving silently after those bonuses). The Rogue will also have his choice of 10th level special abilities, rather than being stuck with improved evasion.
So, bottom line, the class you've made has no real flavor. It's not unbalanced, but its prerequisites do not force the character to make interesting choices, and wind up giving him no cool ne abilities that he couldn't have gotten otherwise. Hope this doesn't sound too critical, but I think you were begging for some analysis.