Last Epoch Yrun Bug in Season 5 had two forms before Hotfix 1.5.1.1: Yrun could create invisible damaging zones, and the endgame version could spawn outside Empowered Monoliths. Both are fixed in the October 3 build.
The invisible-damage issue is the more dangerous one because it can look like unexplained incoming damage instead of a readable boss mechanic. Update before changing defenses or assuming your build is being hit by an intended hazard.
Last Epoch Yrun Bug: invisible damage fix
EHG says Yrun could spawn invisible damaging zones. The damage was real, but the visual information needed to read the danger was missing.
Hotfix 1.5.1.1 corrects that Last Epoch Yrun Bug, so the fight should no longer punish you with an unseen ground effect. A visible hazard after the patch is normal encounter information.
Wrong endgame spawn fix
The second Last Epoch Yrun Bug affected location. Endgame Yrun could appear outside Empowered Monoliths, putting that version of the boss into content where it was not intended to exist.
After 1.5.1.1, endgame placement should respect the Empowered Monolith boundary again.
How to verify the hotfix
Close Last Epoch completely and install the newest client. EHG explicitly says the build requires an update, so remaining in an old session is not enough.
For Last Epoch Yrun Bug, the clean test is entering the relevant Monolith content on the new version and checking both the hazard visibility and encounter location.
If invisible damage remains
Record the moment it happens and rule out another enemy or effect. If the source is genuinely invisible on 1.5.1.1, use F8 and include the zone, timeline and any video you can provide.
A repeatable Last Epoch Yrun Bug after the listed fix is valuable information because the original invisible-zone issue is marked resolved.
Does the hotfix nerf Yrun?
No balance change is listed. The build does not say Yrun lost damage, health or mechanics. It fixes visibility and placement.
If the fight is now readable but still difficult, that is not the same Last Epoch Yrun Bug. Treat it as a build or execution problem rather than waiting for another version of this fix.
Why placement matters
Endgame routing depends on encounters appearing in the content tier where their difficulty and rewards belong. Fixing the wrong-location spawn keeps that progression cleaner.
The best response to Last Epoch Yrun Bug is therefore simple: patch first, then judge the encounter on the corrected version.
How to tell the invisible-zone bug from normal boss damage
Yrun can still deal legitimate damage after the hotfix. The important difference is whether the arena gives you a visible effect or readable attack that matches the damage you receive. The fixed issue involved a damaging zone with no visible warning, so a clearly telegraphed hit is not evidence that the same bug remains.
Watch the ground immediately before your health drops. If you can see the effect and consistently move out of it, the mechanic is functioning. If health disappears in an apparently empty area on the corrected build, capture that moment for a report.
Why you should not change your build first
Invisible damage can make a character feel under-defended even when the real problem is missing visual information. Before 1.5.1.1, stacking more health or resistance would not make the hazard readable. Updating the client removes that uncertainty and lets you evaluate the fight on the intended information.
Once the arena is displaying correctly, normal defensive tuning makes sense again. Until then, build changes can hide the symptom without fixing the actual encounter problem.
Official source: Eleventh Hour Games Hotfix 1.5.1.1 notes.
