At the end of a Greater Rift, a legendary gem will drop until you have them all on your current character. You level legendary gems by advancing through higher and higher Greater Rifts. There are currently 20 legendary gems, including the Season 4 legendary gem, Bane of the Stricken.

At rank or level 25 of a legendary gem, a second effect activates for the player to use, though the first effect continues to increase with each rank. A legendary gem has a unique effect that increases with the gem’s rank. Legendary gems can only be socketed into jewelry slots - amulet and each ring - so you can only have three equipped at one time. Legendary gems aren’t ordinarily colored gems that provide a flat or single percentage stat when socketed into armor.

Zoltun Kulle brought a second trio of build items to the game with Kanai’s Cube, where you can equip three legendary powers which you’ve previously extracted from their items. But Seasons were introduced a little over a year ago with patch 2.1, and they brought with them the first build trios to remember - legendary gems.

Diablo 3 best legendary gems for wizard