A hidden hardcore version of the Z-Rex boss fight has been discovered in Call Of Duty: Zombies‘ Shattered Veil map, and it only activates after reaching round 100. This secret fight ramps up the difficulty dramatically, transforming the already intense Easter egg finale into a relentless test of skill, speed, and survival. With faster enemy spawns, an enraged Z-Rex, and zero room for error, it’s one of the toughest challenges Treyarch has ever hidden in a Zombies map.
How to trigger the hidden Z-Rex hardcore boss fight in Shattered Veil
Call of Duty: Zombies players have uncovered a brutal secret inside Shattered Veil. It turns out the Z-Rex boss fight has a hidden hardcore version that only activates under one condition: reaching round 100 before initiating the final battle.
The normal Z-Rex encounter is already a tough three-phase fight filled with non-stop zombie pressure. But this hidden version completely changes the pacing and mechanics, pushing even experienced players to their limits.
To unlock it, you must first complete every step of the Shattered Veil Easter egg. Once you’re ready to trigger the final fight, do not activate it until you’re on round 100 or higher. If you enter the fight at round 100+, a special sequence plays during the second phase. The arena lights turn green, the “fetch me their souls” audio cue plays, and you’re suddenly facing a version of Z-Rex that behaves like he’s fully enraged from the start.
The best round 100 strategy in Shattered Veil
Reaching round 100 isn’t easy, especially if you’re trying to prepare for the boss fight at the same time. But one method stands out as the fastest and safest route right now.
Players are locking down a spot near Pack-a-Punch in the underground airlock. Using the Wonder Waffe DG-2, this area can be held with little Movement as zombies approach from only three predictable angles: from below your feet, on the left side, and in front near a fence.
Using perks like:
- Vulture Aid
- Deadshot Daiquiri
- Death Perception
…along with the right augments, you can regenerate ammo as you kill zombies. This setup lets players hold position almost indefinitely without running dry on the Wonder Weapon.
Most players report getting to round 100 in just over 2 hours using this method. But remember: you must finish the Easter egg steps before round 100, or the boss won’t be available to activate.
Learn more about the hidden Z-Rex boss mode from MrDalekJD on YouTube.
What changes in the hardcore Z-Rex fight
Once you activate the Z-Rex fight at round 100+, things look the same—at first. Phase one plays out normally. But midway through phase two, the sky changes to an ominous green hue, and you hear the familiar sound cue from a special round. That’s your warning. You’ve triggered the hardcore variant.
From here on out, Z-Rex behaves like he’s already in his final phase:
- He moves extremely fast
- His tracking is nearly instant
- He never pauses between attacks
- Toxic zombies spawn at an accelerated rate
You’ll feel overwhelmed almost immediately. The boss charges nonstop, sometimes chaining his attacks with little to no delay. He also returns to his feet faster after being stunned or staggered. This makes the arena significantly harder to navigate without getting pinned.
Ammo management becomes even more crucial. Picking up drops is risky under pressure, and the smaller window of downtime between attacks leaves no room for error. Using tools like the Kazmir, field upgrades, or even a Chopper Gunner becomes essential.
Footage confirms it’s a real secret boss mode
Popular Zombies creator JCbackfire posted a full video of his run, including the moment the boss fight shifted into hardcore mode. In his gameplay, you can see the arena change, Z-Rex’s sudden aggression, and the wave of tougher zombies flooding the arena.
Even with nearly a million points saved, full perks, and power-ups like Raindrops and Chopper Gunner, JC found himself constantly cornered and running low on options. During the final phase, he had no self-revives left and nearly failed the run when his Chopper Gun ran out.
This clearly isn’t just a cosmetic change. The mode fundamentally shifts how the boss behaves and how zombies react in the arena.
Developer confirms this mode exists—and issues a challenge
Following the buzz around the secret fight, a Treyarch developer confirmed on Twitter that this is a built-in feature. He called it the “hardcore Z-Rex mode” and said it’s his personal favorite way to play.
Even more interesting, he challenged the community to try completing it in a four-player co-op using melee-only weapons. While this might sound impossible, the challenge may hint at a hidden reward or deeper Easter egg tied to that specific method.
Whether there’s an undiscovered reward or not, the community is now digging deeper into the map, looking for hidden triggers, bonus loot drops, or changes to the post-boss cutscene. As of now, no unique loot has been confirmed for completing the fight at round 100, but that could change if new discoveries are made.
What could be next for Shattered Veil Easter eggs?
Treyarch has a long history of hiding layers of secrets inside their Zombies maps, and this latest hardcore boss variant only reinforces that. While the community thought the Easter egg was fully solved, it turns out there was one more surprise waiting for those brave enough to go beyond round 100.
JCbackfire himself speculated in the video that something more might be hiding behind this mechanic. He suggests it’s possible that completing the fight under certain conditions—like the melee-only challenge—could trigger another layer of the Easter egg or a secret ending.
If you’re attempting the Shattered Veil Easter egg and want to speed up the process, JC also uploaded a tips and tricks video to help with shortcuts, item spawns, and efficient step progression.
Secret Z-Rex boss fight in Shattered Veil FAQ
How do you trigger the hardcore Z-Rex boss fight?
Reach round 100, then activate the boss fight as normal.
What changes in the hardcore boss mode?
Z-Rex stays in enraged final-phase mode the entire fight.
Is there a reward for finishing the boss on round 100?
Currently, no special reward is confirmed.
What perks should I use to reach round 100?
Use Deadshot Daiquiri, Death Perception, Vulture Aid, and stamina-based perks.
Can this be done in co-op?
Yes, and there’s a melee-only 4-player challenge suggested by Treyarch devs.
How long does it take to reach round 100?
With the Wonder Waffe method, around 2 to 2.5 hours.
For players wanting the toughest Zombies challenge yet, this hidden Z-Rex fight is now the top-tier test. If you manage to survive it, you’ve officially beaten one of the hardest hidden bosses in Call of Duty history.
Stay tuned for future updates or possible discoveries around this boss fight from CODIntel. And if you’re planning to attempt the melee-only challenge, good luck—you’ll need it.
