The Archon: Secrets

Rampage Inducer

On The Archon, the Rampage Inducer is hidden in the Temple itself. Five bull skulls must be shot in order; any weapon works, and each one bursts into flames when it is hit.

Above the Mystery Box spot on the left of the courtyard, as the game starts.
Above the zombie spawn in the middle of the Temple.
Above the SVT-40 wall buy.
High on the wall in the middle, just before the Pack-a-Punch area.
Above the Pack-a-Punch Machine.

The Rampage Inducer, a stone glowing red under the tree of the Temple, with its deactivate prompt, The Archon, Call of Duty Vanguard Zombies

The stone

It appears at the foot of the tree facing the Pack-a-Punch. Once activated, zombies spawn faster and move faster.

Solo and co-op

In solo it can be turned on and off at will; in co-op every player has to vote for it.

Round 55

At the end of round 55 it shuts down for good and explodes.

Mister Peeks and the Ray Gun

Activate the Rampage Inducer and get a shovel.
Every five rounds a scream is heard: a dark dig site has appeared somewhere on the map, and a child can be heard laughing near it.
Dig it up to get a part of Mister Peeks, the bunny of the Mystery Box. A site missed during its round comes back five rounds later.
With the third part, a Ray Gun appears along with several Bonus Points power-ups.

Vanishing Shore, the hidden song

Upstairs in the Radio Outpost, in East Spring, an instrument leans against the wall to the left of the hole in the floor. Interacting with it three times plays three chords, then Vanishing Shore, the orchestral version of A Light from the Shore by Kevin Sherwood first heard on Tag der Toten.

Radios

Twelve radios are hidden around the map. Their recordings tell the past of the Construct and of the Archons before Kortifex.