Diablo 4's adding a wave-based roguelite mode in Season 5

pcgamer.com:

Diablo 4's fifth season will have an interesting-sounding new mode—an activity called Infernal Hordes that's something like a roguelite. Using an item called in Infernal Compass, players will be able to enter the Realm of Hatred and fight timed waves of enemies. Those enemies will drop burning aether, and between waves you'll be able to choose «Boons & Banes» that let you get more aether. 

Get through enough waves and you'll fight the Fell Council, a group of three randomly selected from a pool of five minibosses. Beat those and you'll get to spend your burning aether on the Spoils of Hell: Equipment, Materials, Gold, and Greater Equipment—which guarantees an item with a powerful Greater Affix.

Infernal Hordes will be available to test on the Diablo 5 Public Test Realm from June 25 to July 2, per Blizzard's What You Need To Know post on the subject.

The Infernal Compasses used to take on an Infernal Hordes challenge will be gotten by clearing endgame bosses, Helltides, Nightmare Dungeons, and Whispers. There'll be eight tiers of Infernal Compasses reached by upgrading your compass using scrolls found in the game, with higher tiers of compass sending you up against harder enemies in Infernal Hordes for commensurately higher reward.

The seasono 5 test realm will also have quality of life improvements to endgame bosses, making them easier to fight in succession by letting you do it without resetting the dungeon. There are also quality of life boosts to Helltide, Whispers, loot, and treasure goblins, and a tweak that'll let more classes use more kinds of weapons. There are also auto-pin, audio navigation, and on-screen compass accessibilty features on the way.

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