Sentinel Artifacts

Sentinel Artifacts are an in-game mechanic introduced in the Call of Duty: Black Ops 4 Zombies map Voyage of Despair, and are also present in IX during the intro cutscene, and are in-game in Dead of the Night. They are exclusive to the Chaos story, and are effectively the Chaos story's replacement for the Power mechanic in the previous Aether story.

Gameplay
Sentinel Artifacts essentially work as the Chaos story version of Power, as many areas of a map cannot be opened up until the Sentinel Artifact is activated, similar to Power. The difference between the 2, however, lies in the fact that the Artifact is not necessary to buy Perks. However, Pack-A-Punch cannot be activated without the Sentinel Artifact (in the case of maps with the Sentinel Artifact). The Sentinel Artifact is located in the following locations for each map:

Voyage of Despair - Located on the Poop Deck.

Dead of the Night - Located in the Grand Staircase.

Story
The Sentinel Artifacts were created by the mysterious group known as the Nine in order to harness and protect the power of Prima Materia. When activated, the Artifacts will begin a Trial that will test the worthiness of an individual, through battling the undead and other creatures. Once activated, an individual cannot leave a Trial unless it is fully completed, or the individual is killed. The Sentinel Artifacts are each based off of a specific God of a mythology, with the Artifact on Voyage of Despair corresponding to Odin, the Artifact in IX corresponding to Ra, and the Artifact in Dead of the Night corresponding to Danu.

The Danu Artifact, at some point, came into the possession of Alistair Rhodes, until it was stolen by his butler, Godfrey, and the enigmatic religious group known as "The Order" during a house party in Alistair's manor. The Artifact was activated, transforming the guests of the Rhodes Manor into Zombies, Nosferatus, Catalysts, and Werewolves. Soon after, Godfrey, Jonathan Warrick, Christina Mirela, and Gideon Jones completed the Trial set forth by the Danu Artifact. However, Godfrey murdered the other 3 members before he was subsequently shot to death by Scarlett Rhodes, the daughter of Alistair.

Soon after Alistair's kidnapping, as requested by him, Scarlett gathered 3 of Alistair's most trusted companions; Stanton Shaw, Diego Necalli, and Bruno Delacroix. The group of 4 traveled onto the Titanic in order to gain the Odin Artifact, until it was subsequently stolen and activated by a member of the Order. Afterwards, the 4 began the Trial for the Artifact and completed it. They were then shown a vision of Delphi, Greece, where they would be able to find the Oracle and learn more about the Order that they faced off against.

The group soon arrived in Delphi, and spoke to the Oracle. They then inhaled an unknown vapor that allowed the group to travel into the bodies of individuals in the past. There, they were transported to a gladitorial arena in the Roman Empire, where they were forced by the Order, and their leader, the High Priest of Chaos, to complete the Trial of Ra. They were then, in those bodies, executed by the Order.