Diablo 4 season 10, titled Season of Infernal Chaos, is going live on September 23, and Blizzard has confirmed which features are strictly seasonal and which will stick around after the season ends.
In a blog post breaking down the new season, Blizzard reveals a change to boss fights that people have been asking for since Diablo 4 launched back in 2023. If you've played much of Diablo 4, you'll know some bosses have scripted events in which they become immune to attacks. The idea is to space out the boss fights long enough that players have to deal with their unique mechanics, but it often leaves high-level players standing around waiting for the immunity to pass so that they can kill the sucker and grab their loot.
That's going away, permanently. Starting with season 10, the invulnerability phase will only start after a player has spent 10 seconds fighting a boss, meaning the phases "can now effectively bypassed [sic]" if you're powerful enough.
However, these bosses will now get damage shields when they're at 2/3 and 1/3 life that last five seconds and have 1/3 and 2/3 of the boss's life, respectively. Thankfully, if you manage to break the shield while it's active, that doesn't bring back the boss's invulnerability phase.
In addition to this seemingly wonderful change, the list of permanent changes being introduced in season 10 include the newly "reborn" Infernal Hordes, Chaos Waves, changes to the Infernal Hordes' Fell Council, the new Bartuc boss, all new Uniques, and some "base offering adjustments," all of which you can read about in much greater detail in the blog.
Meanwhile, season 10 changes that won't be permanent include Chaos perks, Chaos armor, Chaos Rifts, Chaos Rift Nightmare Dungeons, Fleeting Hordes, Viz-Jaq'taar Seasonal Reputation, and naturally, the seasonal questline.
Related: Blizzard wakes up and chooses fun: the "wacky and crazy" powers of past Diablo 4 seasons could come back as "permanent" features
