ESO Murky Grotto Secret Boss: How to Get Fungal Vision

The ESO Murky Grotto Secret Boss is Toxic Matron, a hidden enemy found in the Arcanum Wing of the Nowhere Vault. Unlike most encounters in The Elder Scrolls Online, defeating enemies as quickly as possible can actually prevent this boss from appearing. Instead, you need to survive the room’s poisonous environment while keeping the encounter active long enough to trigger the hidden objective.

Murky Grotto also connects to a larger secret involving Hunt of the Watchers and Fungal Chasm. Completing these objectives allows you to obtain Fungal Vision, an effect needed to uncover another hidden route within the Vault. There are a few important conditions to understand before attempting the boss, particularly if you have already cleared the room without seeing Toxic Matron.

How to Spawn the ESO Murky Grotto Secret Boss

To summon Toxic Matron, you need to activate the plant in Murky Grotto and survive the poisonous encounter without killing the toxic plants or ending the enemy waves too early.

The encounter is an endurance challenge rather than a traditional fight. Although enemies appear throughout the room, clearing them immediately can end the event before its secret objective becomes available.

You should also obtain Watcher Filtration Gills from Hunt of the Watchers before attempting the hidden encounter. Player testing indicates these are required to successfully spawn Toxic Matron.

How to Get Watcher Filtration Gills

Watcher Filtration Gills are obtained through the secret objective in Hunt of the Watchers, another challenge room within the Arcanum Wing.

Complete the room’s normal objective, but remain inside rather than taking the exit. Find the whistle resting on one of the hills, then identify the remaining Watcher marked with a green symbol.

Lure this Watcher towards the green sigil near the starting area and activate the sigil to remove its immunity. Once the enemy becomes vulnerable, defeat it and collect the gills.

You can find the full instructions in our ESO Hunt of the Watchers Puzzle Guide.

Several players have reported being unable to summon Toxic Matron without the gills. Although ZeniMax has not explicitly confirmed this prerequisite in its published patch notes, obtaining them first is supported by player testing and avoids wasting a Murky Grotto attempt.

ESO Murky Grotto Secret Boss: Toxic Matron Walkthrough

Once you reach Murky Grotto with the Watcher Filtration Gills, follow these steps to trigger the secret boss.

1. Locate the central plant, known as the Toxic Bud, and interact with it to begin the encounter.
2. Remain on or immediately around the activated plant rather than moving across the room to fight enemies.
3. Allow the enemy waves to continue spawning. Avoid clearing them completely and leave the toxic plants alive.
4. As the poison intensifies, remain inside the damaging area that develops around the plant.
5. Use healing abilities, shields and defensive buffs to survive the damage without abandoning the area.
6. Continue surviving until Toxic Matron appears, then defeat the boss to unlock Fungal Vision.

The toxic plants are particularly important. Killing them can interfere with the hidden objective, so avoid using abilities that automatically damage nearby enemies.

For this encounter, leaving the enemies alone until Toxic Matron appears is generally more reliable than trying to control each wave through combat.

How Long Does Toxic Matron Take to Spawn?

The ESO Murky Grotto Secret Boss can take approximately three minutes to appear, according to players who have completed the hidden encounter. This is an observed duration rather than a guaranteed spawn timer.

You may notice dialogue from Urli as the encounter progresses, indicating that the challenge is nearing completion. These comments are useful because they reinforce that Murky Grotto is testing your ability to endure the toxic environment.

Remain close to the Toxic Bud and keep yourself alive while waiting for the boss. The poison damage is an intended part of the encounter, not a sign that you have failed.

Once Toxic Matron appears, you can switch to attacking and defeat it normally.

How to Get Fungal Vision in ESO

Defeating Toxic Matron rewards you with Fungal Vision, the hidden effect associated with Murky Grotto.

Fungal Vision allows you to see concealed features in fungal environments, including a secret staircase in Fungal Chasm.

To use it, enter Fungal Chasm within the Arcanum Wing and look towards the left side of the room from the entrance. With Fungal Vision available, a translucent green staircase becomes visible.

Follow the staircase upwards to reach the hidden area containing the Subjugating Mindspore.

The Mindspore is subsequently used in Prison of the Unrepentant within the Cursed Castle wing, where it contributes to obtaining one of the Vault’s Gryphon Seals.

For the exact staircase location and next objective, see our ESO Fungal Chasm Puzzle Guide.

ESO Murky Grotto Secret Boss Not Spawning: What to Check

If Toxic Matron doesn’t appear, the most likely explanation is that the encounter has ended prematurely or a prerequisite is missing.

Check whether you obtained Watcher Filtration Gills. Players have reported unsuccessful attempts without them, so completing Hunt of the Watchers first is worthwhile.

Make sure the toxic plants remain alive. Damaging abilities with large areas of effect can kill them unintentionally, particularly if enemies gather around the central plant.

Stay inside the poisonous area. Moving away from the Toxic Bud or leaving the damaging circle may interfere with the endurance objective. Healing through the damage is preferable to abandoning the position.

Watch your companions and summoned pets. Some players have reported better results without companions, as they may attack enemies or move around the room during the challenge. This isn’t a confirmed universal restriction, but dismissing them is worth trying if the encounter repeatedly fails.

Avoid cleansing the encounter prematurely. Other player walkthroughs report that remaining inside the poison without using its cleansing mechanic is part of triggering the hidden objective.

ZeniMax also documented fixes for Murky Grotto’s secondary-objective credit during Update 51 testing, particularly where grouped players received incorrect completion credit.

If the encounter ends before Toxic Matron appears, you may need another opportunity to attempt the room. The Nowhere Vault features randomized challenge rooms, so Murky Grotto isn’t guaranteed to appear in the same position on every run.

Where to Go After Defeating Toxic Matron

Once you have defeated the ESO Murky Grotto Secret Boss and obtained Fungal Vision, your next destination is Fungal Chasm.

The connected secret objectives follow this sequence:

1. Hunt of the Watchers: Obtain Watcher Filtration Gills.
2. Murky Grotto: Survive the poison encounter and defeat Toxic Matron to obtain Fungal Vision.
3. Fungal Chasm: Reveal the hidden green staircase and collect Subjugating Mindspore.
4. Prison of the Unrepentant: Use Subjugating Mindspore for the Cursed Castle Gryphon Seal objective.

You won’t necessarily encounter these rooms in that order, so you may have to revisit the relevant challenge rooms during later runs.

The ESO Murky Grotto Secret Boss is easy to miss because the normal instinct to eliminate enemies works against the hidden objective. With the Watcher Filtration Gills obtained beforehand, keeping the toxic plants alive and surviving the poison gives you the opportunity to summon Toxic Matron.

Defeating the boss unlocks Fungal Vision and opens the way towards the Subjugating Mindspore, bringing you another step closer to completing the Nowhere Vault’s hidden seal objectives.

Official source: ZeniMax Online Studios, Update 51 PTS Patch Notes v12.1.2.