Guardian Feat

You excel at holding enemies in place and punishing attacks against your allies.

Prerequisite: None

• Punishing Strike. When a hostile creature within 5 feet of you strikes an allied creature other than you within 5 feet, you can use your reaction to make an opportunity attack against that target.
• Halting Blow. When you hit a creature with an opportunity attack, the creature's speed becomes 0 until the end of the current turn.

Source: KT