Rogue: Shadow Blade

Here is my take on what I call a Shadow Blade.  The class mixes up some of the shadow monk abilities with the champion fighters, yet is has its own flare.

I had ninja in mind when making this class. Not fully a ninja but I like it none the less.

3rd Level:

Defensive Intellect: While wearing no armor and not wielding a shield your AC equals 10 + your Dexterity modifier + your Intelligence modifier.
Slow Fall: Same as the monk ability in PHB.

9th Level:

Cloak of Shadows: When you are in an area of dim light or darkness, you can use your action to become invisible. You remain invisible until you make an attack, cast a spell, or are in an area of bright light.

13th Level:

Eye for Devastation: Your weapon attacks score a critical hit on a roll of 19 or 20.
Puff of Smoke: You may use your action to transform into a puff of smoke. You become the target of the Gaseous Form spell.

17th Level:

Double Strike:Whenever you score a critical hit on your turn you may use your bonus action to make another attack, this attack is made with disadvantage. If you hit with this you may apply your sneak attack damage even if you used it already this turn.