Strangler

You’ve developed the necessary skills to efficiently strangle an opponent. You gain the following benefits:

• You can use your action to strangle a creature grappled by you. To do so, make another grapple check. You can also use your action to strangle a creature that is paralyzed, stunned, or unconscious (no grapple check required). 
• A creature that is being strangled must succeed on a Constitution saving throw (DC 8 + your proficiency bonus + your Strength modifier) to remain conscious. If you strangle an unconscious creature it immediately begins to suffocate. 
• A creature that is suffocating can survive for a number of rounds equal to its Constitution modifier (minimum of 1 round). At the start of its next turn, it drops to 0 hit points and is dying, and it can't regain hit points or be stabilized until it can breathe again.