Ahead of the Curve: G'huun
Defeat G'huun in Uldir on Heroic difficulty or higher, before the release of the next raid tier.
10/23/2018
Ahead of the Curve: Xavius
Defeat Xavius in the Emerald Nightmare on Heroic difficulty or higher, before the opening of the Nighthold.
11/16/2016
Ahead of the Curve: Imperator's Fall
Defeat Imperator Mar'gok atop his citadel in Highmaul on Heroic difficulty or higher, before the release of patch 6.2.
12/23/2014