The Mother's Triune offer you power, believing you to be Sanctuary's last hope against the forces of Hatred.

What to expect in Season of the Infernal Hordes

• New Questline: Harness demonic power with new character, Istel.
• New Dungeons - Hellbreaches: Hell itself is pulled into Sanctuary in these new risk/reward dungeons.
• The Infernal Hordes: A new challenge awaits in World Tier 3! Face against the endless hordes of Hell.
• All new Season Journey: Conquer 7 Chapters of challenges.
• 22 new Legendary Aspects & 10 new Unique Items: Explore new ways to build and play each Class. All new Aspects and Uniques have already been incorporated in our Build Planner and Farming Tools!
• All new Cosmetics: Acquire seasonally themed looks in the Battle Pass and other new looks in the Shop.

Hellbreaches

Datamined info shows us that Hellbreaches are a new dungeon with high risk and rewards. Not much is known about Hellbreaches apart from the fact that you will also be able to gather Burning Aether from these dungeons too.

Collect Burning Aether from Hellbreaches and Infernal Hordes in Torment

Demonic Powers

Some other assets have also emerged from datamining the season 5 PTR. These are referenced as Aspects, and could refer to the "Power offered by The Mother's Triune".

How these powers will be incorporated in the game is not known yet. There are however hints at special shrine effects that are empowerd with the Mother's Gift.

Infernal Channeling Shrine: You wield demonic power. Enemies drop Mother's Gift. Your Skills cost no Resource and have lower Cooldowns. Increased attack speed and chance to reset cooldowns.

Mother's Gift

Mother's Gift will be the new Season 5 Reputation Currency. Mother's Gifts drop from slaying powerful servants of Hell, including Elites, Champions, Hellborne, and Bosses.

In the game file, there is a file called Reputation_S05_Cultist_Helltide_Reputation indicating some Helltide variant for this season.

While these hints are in the PTR build right now, it doesn't mean that these unanounced features will actually be released.