Diablo 4 Season 10 locks in permanent boss fixes as invulnerability phases can be skipped

Blizzard has detailed what’s seasonal and what’s here to stay in Diablo 4’s Season 10, “Season of Infernal Chaos,” which goes live on September 23. The headline change: lair bosses’ invulnerability phases are being reworked so high-DPS groups can push through without waiting out long, forced downtime.

What’s permanent (Seasonal + Eternal Realms)

• Infernal Hordes updates, including Chaos Waves and changes to the Fell Council.
• A new Bartuc boss fight folded into the core rotation.
• Base Offering adjustments to smooth run-to-run choices.
• A fresh wave of Uniques for every class.
• System-wide changes to lair boss invulnerability.

How the boss changes work

Until now, many lair bosses flipped into scripted “can’t hit me” phases that stretched out kills and made farming feel stop-start. Starting in Season 10, those invulnerability windows can’t trigger for the first 10 seconds of the fight, which means strong parties can burn through thresholds before the immunity ever appears. When bosses hit two-thirds and one-third life, they now raise short, five-second damage shields instead: the first worth one-third of max HP at 2/3 life, and the second worth two-thirds of max HP at 1/3 life. Break the shield during its short uptime and the boss does not become invulnerable—no more standing around waiting.

Blizzard’s patch notes reinforce the approach on the season’s featured fight, noting that Bartuc no longer goes invulnerable and instead follows the new shield mechanic shared across lair bosses. In practice, the shift turns high-end bossing into a cleaner DPS-check: push, pop the shield, delete it, keep going. For lower power levels, the five-second window still gives room to reposition and deal with mechanics without turning the encounter into a slog.

What’s seasonal-only (won’t persist after Season 10)

• Chaos Perks and the Viz-Jaq’taar Seasonal Reputation track.
• Chaos Armor (it reverts after the season ends), plus Chaos Rifts and Chaos Rift Nightmare Dungeons.
• Fleeting Hordes and the Season 10 questline.

Why it matters

The invulnerability overhaul directly targets one of the most common community complaints since launch: wasted time during boss farming. By tying immunity to a brief shield check—and by delaying any invuln trigger for the opening 10 seconds—Blizzard preserves encounter shape without punishing efficient groups. The studio is also using Season 10 to permanently deepen its endgame loop: Infernal Hordes are “reborn,” Chaos Waves become a core modifier, the Fell Council gets a new role, and Bartuc enters the boss table for good. Together, those changes mean even players who skip seasonal grinds on Eternal will feel real upgrades in their day-to-day runs.