Dungeons & Dragons 5e Element 133 Class Feature: Careful Approach

Your stealth approach gives you several benefits. You have advantage on any Dexterity (Stealth) check and on the first weapon attack made on your turn if you move no more than half your speed on the same turn. All attacks against a suprised creature become deal critical damage if they hit.

Ambush Tactics

You learn how to use the environment to better ambush, escape and kill your enemies. While in your Favored Terrain, you gain advantage on your Dexterity (Stealth) checks, and your targets make Wisdom (Perception) checks to detect you at disadvantage.

In addition, if you make an attack while hidden and miss, your position is not revealed.