Sentinel¶

Armored warrior raising a shield to guard against approaching enemies

Source: Player's Handbook

You gain the following benefits.

Ability Score Increase.
Increase your Strength or Dexterity score by 1, to a maximum of 20.

Guardian.
Immediately after a creature within 5 feet of you takes the Disengage action or hits a target other than you with an attack, you can make an Opportunity Attack against that creature.

Halt.
When you hit a creature with an Opportunity Attack, the creature’s Speed becomes 0 for the rest of the current turn.