Analyzing the yeth hound makes me wonder: The description of pass without trace says it creates “a veil of shadows and silence” that boosts Stealth checks. Clearly it dampens sight and sound, but what about smell? Also, is a yeth hound's Keen Hearing and Smell trait considered a "magical means" of tracking, or does that phrase refer only to scrying and similar spells?

— Keith Ammann 🔜 C2E2 (@KeithAmmann) February 17, 2020

Pass without trace does just what it says, it adds to Dexterity (Stealth) checks and blocks nonmagical tracking. Smelling isn’t magical unless it fits the criteria for being magical as outlined on page 18 of the the Sage Advice Compedium. https://t.co/9yInWpY9vG pic.twitter.com/lRrm2ua7lf

— Dan Dillon 👥 (@Dan_Dillon_1) February 17, 2020

OK, so the “veil of shadows and silence” is ribbon text not meant to be taken literally, and a yeth hound can’t use its Keen Hearing and Smell to track a target under pass without trace. Which leads to the question …… what is "tracking"? Can a yeth hound continue to pursue a creature that never leaves the range of its hearing and smell? Does tracking imply that you start without target lock, then acquire it once you find tracks? Or does it refer to any kind of active pursuit, e.g., a chase?

— Keith Ammann 🔜 C2E2 (@KeithAmmann) February 17, 2020

Tracking means following something’s trail, or “tracks.” It doesn’t refer to something you can currently perceive.

See DMG pg 244 for the rules on Tracking.

— Dan Dillon 👥 (@Dan_Dillon_1) February 17, 2020

Got it. So IOW, in order to elude the yeth hound once it sniffed you out, even under pass without trace, you’d have to get beyond the range of its hearing and smell. But PWT might also keep it from sniffing you out in the first place, and therefore from pursuing you if you ran. Looks solid. If it can see you, it can just see you. You're right there, it's not tracking, it's just looking at you.

If you get out of direct sight/hearing, then it's got to rely on tracking, which pass without trace foils.

— Dan Dillon 👥 (@Dan_Dillon_1) February 17, 2020