Diablo 4 Season 1 is coming in two weeks with special gems for "stupid, broken new builds"

gamesradar.com:

Blizzard has announced Diablo 4 season 1, titled Season of the Malignant, launching on July 20.

Blizzard says Diablo 4's first season is designed to "appeal to everything a player does in Diablo 4," explains lead producer Tim Ismay, allowing you to "build your character in a different way." The core theme of the season is the titular threat, "the Malignant," which "shows up throughout the entire game."

The way it works is, every time you encounter an elite monster, there's a chance it'll spawn as a malignant version of that same monster, featuring some gross growths that grant it additional powers. If you manage to beat it, it'll drop a heart, and interacting with it using Cage of Binding will kick off a ritual that pulls in all Malignants and spawns an even more powerful version of the enemy, complete with minions. Beat that and you'll get the Caged Heart, which Blizzard describes as a new item comparable to Legendaries but "a little bit more."

Caged Hearts pack "an enormous amount of power," and just like gems you can slot them into gear to build "stupid, broken new builds," in the words of Ismay. There will be four different types of Caged Hearts, one of which will be of the rarer, omni-colored variety.

While you'll be able to earn Caged Hearts through random encounters, there will also be more targeted opportunities via Malignant tunnels, which will have ways for players to use Invokers to summon Malignants of different varieties and get the Caged Heart they're gunning for, or at least have a much better shot at it.

Blizzard also broke down the Diablo 4 battle pass for season 1, which it has repeatedly made clear is totally optional and separate from the normal campaign, or what the studio calls "the Eternal realm."