Dungeons & Dragons 5e Element 133 Class Feature: Sneak Attack

Beginning at 1st tier, you know how to strike subtly and exploit a foe’s distraction. Once per turn, you can deal an extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must have a light, finesse, or a ranged weapon property.

You don’t need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn’t incapacitated, and you don’t have disadvantage on the attack roll.

The amount of the extra damage increases as you gain tiers, as shown here.