Blizzard
P.S. While the ‘Ahead of the Curve’ & ‘Cutting Edge’ Feats of Strength are going away when Season 4 launches, the Carcinized Zerethsteed (from killing Heroic Jailer), as well as the 100% Droprates from the Mythic Sylvanas and Mythic Jailer mounts aren’t going away until Dragonflight launches (The Sylvanas and Jailer mythic mounts will stay in the game, but be significantly reduced in droprate as with previous expansions).