Kessime's Legacy is a Unique Pants in Diablo IV Season 15. It drops from Andariel (Echo of Andariel).
Unique power
Blood Wave now forms a wave on each side of you. Both waves converge at your feet, Pulling In all surrounding enemies and exploding for [375 - 450] damage.
Affixes
+3.0-8.0% Cooldown Reduction
Where it drops
Random world drop / any Lair Boss (one guide: 'drops at any Difficulty Tier, increased drop rate per Torment tier'); 3.2.1: all Uniques drop from level 1 in any Difficulty; targetable via Horadric Cube reroll