Hearing a huge “BOOM” followed by a deep roar every few minutes while exploring Mammon at night? And then the whole screen gives you a little shake?
You’re not going crazy, and there’s not necessarily another boss hiding around the corner.
The strange sound near the High Lord’s Courtyard Beacon is a piece of Mammon’s environmental atmosphere: a distant catapult is firing and hitting the castle/fortifications.
What Is the Loud Boom in Mammon at Night?
The recurring explosion-like sound in Mammon is caused by the catapult bombardment happening in the region.
Players have reported hearing it repeatedly at night, especially around the High Lord’s Courtyard area. The sound can be loud enough to make it seem as though a boss, enemy or hidden event is happening right next to you.
It isn’t.
The catapult is part of the Mammon environment, and the game uses the distant impacts to make the region feel like an active battlefield. Community guides also place a catapult near the beginning of the Mammon region, around the Outskirts of Mammon, confirming that siege equipment is physically present in this part of the world.
Why Does It Happen Mostly at Night?
This is the part that makes the sound particularly confusing.
Players have noticed that the boom and screen shake are especially noticeable during Night Mode, leading many to wonder whether the effect is connected to a hidden nighttime event.
There is currently no solid evidence that the nighttime bombardment unlocks a secret quest, boss or collectible.
Instead, it appears to be an ambient world effect associated with Mammon’s siege atmosphere.
Night Mode itself also changes other aspects of Mammon’s exploration. For example, the Collector appears near the Abandoned Outpost specifically under the harder nighttime conditions.
So the fact that you’re hearing the bombardment at night doesn’t automatically mean you’ve discovered a secret objective.
Why Does the Screen Shake?
The small camera shake makes the distant artillery feel much closer than it actually is.
The game isn’t necessarily telling you:
“Something is attacking you.”
It’s more like:
“Something huge just hit somewhere in the distance.”
That environmental trick is especially effective in Mammon because the region is built around ruined strongholds, courtyards, keeps and other remnants of a larger conflict.
Is There an Enemy or Boss Causing the Sound?
No confirmed enemy or boss is associated with the recurring boom.
This is important because Mammon contains plenty of actual threats, including optional encounters and major bosses. The High Lord’s Courtyard route eventually leads into the Royal Crypt and the Vellen, High Lord of Mammon encounter, with Lazlo’s Shell located beyond the boss arena.
But the recurring distant boom isn’t Vellen attacking you from somewhere off-screen.
It’s environmental audio.
Is It a Secret Event?
At the moment, there is no reliable evidence that the nighttime boom triggers a secret event.
Players have already tried following the sound and searching around the High Lord’s Courtyard, but the community hasn’t found a hidden interaction tied to it.
That matches the most straightforward explanation from the discussion: the castle is simply being hit by a catapult.
So you don’t need to spend half an hour running around Mammon trying to locate an invisible boss.
Where Can You Hear It?
The sound is particularly noticeable around:
Mammon → High Lord’s Courtyard
Players also report hearing it elsewhere in Mammon, depending on where they’re standing and how the environmental audio is carrying.
The High Lord’s Courtyard Beacon is a particularly useful landmark because it sits close to the route toward the Royal Crypt.
Does It Mean I’ve Missed Something?
Probably not.
If you’ve already cleared the nearby enemies and completed the content available around High Lord’s Courtyard, the booming sound isn’t an indication that you’ve failed to trigger something.
You can safely continue exploring.
The only reason to investigate the area further is if you’re trying to complete the region itself — such as finding Shells, map fragments, dungeons, Tarstones or optional encounters.
For example, Lazlo is found beyond Vellen in the Royal Crypt, so there are legitimate secrets in this area. The catapult sound just isn’t one of them.
What Is Actually Worth Checking Around High Lord’s Courtyard?
If you’re already wondering whether the boom is hiding something, this is a much better use of your time.
Check the Royal Crypt
The underground route from High Lord’s Courtyard eventually leads to Vellen, High Lord of Mammon.
Defeat Vellen and continue through the room behind the arena to find Lazlo’s remains.
Look for the Mammon Map Fragment
A Map of Mammon fragment is also documented near the High Lord’s Courtyard area. Collecting the map fragments helps reveal the region rather than leaving large sections hidden behind fog.
Explore the Nearby Side Areas
Mammon has multiple optional routes and dungeons, so don’t assume the main road is all there is.
The game’s structure intentionally encourages exploring away from the obvious path for Shells, weapons, collectibles and optional encounters.
Is the Boom a Bug?
Probably not.
There’s no strong indication that this recurring sound is a bug or audio glitch.
The fact that players experience it repeatedly and that Mammon actually contains catapult/siege elements makes an ambient bombardment the much more plausible explanation.
Of course, audio bugs can still happen in any game. But if you’re hearing the same deep boom at regular intervals in Mammon, particularly around High Lord’s Courtyard, the intended explanation is the distant siege activity.
Bottom Line
That creepy boom-roar and screen shake in Mammon at night isn’t a hidden boss.
It’s the castle being hit by a distant catapult as part of Mammon’s environmental siege atmosphere.
So when you hear:
BOOM…
and the camera shakes…
you don’t need to start searching every building for a secret enemy.
Carry on.
And if you’re near High Lord’s Courtyard, the things actually worth investigating are the Royal Crypt, Vellen, Lazlo’s Shell and the nearby map/side-content, not the source of the cannon fire.
Quick Answer
Q: What is the loud boom in Mammon at night in Mortal Shell II?
A: It’s a distant catapult impact hitting the castle/fortifications. The sound and screen shake are environmental effects and aren’t currently known to trigger a hidden boss, quest or secret.