Toxic Tyrant (Z-Rex)

The Toxic Tyrant is a World Event in BO7 Endgame featuring the Z-Rex, a massive creature covered in fused rot and fossilized bone from a T-Rex skeleton. It was added to Endgame with the Season One update and takes place in Zone III of Avalon. The event has a two-stage structure: a portal-closing sequence followed by the Z-Rex boss fight itself.

What the Toxic Tyrant is

The Z-Rex is a creature that originated in the Call of Duty: Black Ops 6 Zombies map Shattered Veil. In its Endgame appearance, it is known as the Toxic Tyrant. Its lore origin involves “residual temporal energy” from the Sentinel Artifact creating the creature from a fossilized T-Rex skeleton.

The Toxic Tyrant is one of the harder World Events, especially for lower-CR players.

World Event: Toxic Tyrant

The Toxic Tyrant is a World Event that activates at a random location within Zone III of Avalon. Multiple portals spawn at the event site, with Fear enemies nearby. The event has two separate stages you must complete in order.

Recommended Combat Rating

Zone III content has a recommended Combat Rating of CR 30, but the Toxic Tyrant is among the harder World Events in that zone. A Combat Rating of CR 45+ is typical for this encounter, with multiple players required to deal enough damage to the Z-Rex before the timer expires.

Stage 1: Closing the portals

1. Locate the event area. 10 portals spawn at the event site in Zone III. Fear enemies are present near the portals.

2. Identify and kill HVT Fear enemies. HVT (High Value Target) variants of special Fear enemies spawn throughout the event area. These are marked enemies with higher health than standard enemies.

3. Collect Convergence Artifacts. Each HVT Fear enemy drops a Convergence Artifact on death. Each player can carry one Artifact at a time.

4. Deposit Artifacts into portals. Carry an Artifact to a portal and deposit it. Each portal requires 3 Artifacts to close.

5. Close all 10 portals. Repeat the process across all active portals (30 total deposits across the squad). Coordination among squad members to close them all efficiently is recommended.

Tip

Splitting the squad across multiple portals and assigning deposit duties speeds up the closing sequence significantly. The Z-Rex does not spawn until all portals are closed, so the pace of Stage 1 determines how much time remains for the boss fight.

Stage 2: The Z-Rex fight

Once all portals are closed, the Z-Rex spawns. A timer begins. If the Z-Rex is not defeated before the timer expires, it despawns and the event fails.

Enemy spawns during the fight

Fear enemies continue to spawn during the Z-Rex fight, including Fear versions of Guild Sentinel and Guardian troops. These add-enemies attack players while the Z-Rex fight is ongoing. Have some squad members handle adds while others focus DPS on the Z-Rex.

Caution

The Z-Rex has a very large health pool. Without multiple players at CR 45+ with exotic-rarity weapons, the event timer may expire before the fight is complete. Solo completion is very difficult and not reliable below high CR with an optimized loadout.

Rewards

Defeating the Z-Rex completes the Toxic Tyrant World Event. The Z-Rex drops a briefcase containing an Exotic Skill for players to pick up. Exotic Skills are powerful passive upgrades that extend Combat Rating by 3 when obtained and fully upgraded.

Related pages

World Events All World Event encounters and how they work.

Exotic Skills The reward earned from defeating the Toxic Tyrant.

Combat Rating Recommended CR 45 or higher for this encounter.

Avalon Zone III is where the Toxic Tyrant World Event takes place.

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Data sourced from community research and in-game documentation. Information may change with game updates.