Soul Shards

"With the upcoming 25th Anniversary of the Diablo Franchise, we wanted players to delve into the darker side of the Nephalem's past. In Season 25, players can embrace evil by infusing themselves with the essences of the Lords of Hell. Players will embark on their Season Journey to discover and upgrade demonic Soul Shards based on the seven Lords of Hell. By embodying a Prime and Lesser Evil, players will inflict new forms of pain and suffering on the demons of Sanctuary. We can't wait for players to get their hands on Soul Shards to start unlocking their true power."

- Developer comments

Soul Shards are a type of soulstone.

After the destruction of the Black Soulstone, lingering fragments of the artifact containing the essence of the Great Evils persisted in Sanctuary. These Soul Shards (effectively a type of soulstone) thus contained great power&mdash;the power of the Evils themselves. A number of nephalem were able to find and wield these shards, but they had to be careful, given the allure of such power.

In-game
Soul Shards are Season 25-exclusive socketable-items. Players can find 7 unique Soul Shards, based on the Lords of Hell, which give players demonic new powers. One of 3 Prime Evil Soul Shards can be equipped into Helms and one of 4 Lesser Evil Soul Shards can be equipped into Weapons. Each Soul Shard can be upgraded three times using a new seasonal-exclusive consumable, the Hellforge Ember.

Soul Shards and Hellforge Embers can drop from anywhere in Sanctuary, but Soul Shards have a higher chance to drop from Bosses. Soul Shards cannot be traded, but can be salvaged or utilized in Caldesann's Despair. You may only equip one Prime Evil Soul Shard and one Lesser Evil Soul Shard at a time. Lastly, Soul Shards and Hellforge Embers only drop in Seasonal play, and will not transfer to your non-seasonal character when the season ends.

Prime Evil Soul Shards
The following Soul Shards can be socketed into Helms:

Lesser Evil Soul Shards
The following Soul Shards can be socketed into Weapons:

Ranking
Each Soul Shard starts out with a rank of 0, and they have a maximum rank of 3. Each type of Soul Shard has its own set of legendary affixes. As the gem is ranked-up, stat buffs will increase and more of the affixes will be unlocked.

Caldesann's Despair Recipe
Depending on the rank of the Soul Shard, it replaces the need for a legendary gem.

Trivia

 * Soul Shards are a variation on how Ethereals worked in Season 24. Instead of the affixes being bound to a particular weapon, they are now socketable on any weapon or helm.