@JeremyECrawford Good morning! Can you enlighten us on the Gloom Stalker’s “Dread Ambush” feature and whether it processes per Attack action taken or per Turn? Thank you.

— E’Tallitnics (@ETallitnics) January 7, 2018

Dread Ambusher says, "If you take the Attack action on that turn, you can make one additional weapon attack as part of that action." The extra attack is tied to the action. #DnD https://t.co/xlEYRsm8LL

— Jeremy Crawford (@JeremyECrawford) January 8, 2018

So meaning an Action Surge would grant you another Dread Ambusher Attack, correct? That's correct.

— Jeremy Crawford (@JeremyECrawford) January 8, 2018

It’s futureproofing for the Revised Ranger, which (as of last update) lacks Extra Attack as a basic class feature, right? E.G. it works with Extra Attack now, because all Rangers have EA now, but they may not in the future, hence the very particular wording. the revised ranger has no bearing on the design.

— Jeremy Crawford (@JeremyECrawford) January 8, 2018