The Emerald Mark of Mastery in World of Warcraft is rewarded for completing the achievement, Dragonflight Season 3 Master. The achievement itself is counted as a Feat of Strength, so it doesn't actually award any points, but the Mark of Mastery allows you to buy gear from a vendor in the Emerald Dream.
Speaking of Feats of Strength, you'll get another one for logging into WoW before December 7th. If you pick up the quests, in the Caverns of Time, you can hunt down the 19th-anniversary world bosses to get a mount and some possible gear upgrades for alts. With that said, if you're more interested in gearing up your main, and spending your Emerald Mark of Mastery, here's where to find Theozhaklos, the vendor.
