Shadow (5e Subclass)
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A thief in the night, the Shadow Rogue knows how to kick ass and take names without anyone knowing if they were there.
At 3rd level, as a reaction to an attack, you make a Dexterity saving throw against the enemy's base Strength score or spell save DC, as is appropriate. A cloud of smoke erupts around you. If it succeeds, you successfully dodge the attack, taking no damage. If it fails, you take half.
At 6th level, an an Action, you can vanish from sight, and can use any Action, or Dash. You are revealed when you Attack or do any Action that affects an enemy.
At 9th level, you ignore difficult terrain, and always use standard movement speed no matter what terrain you are on.
At 17th level, on a critical hit, add twice your Dexterity modifier as poison damage. The enemy is now poisoned.