The new Zombies map called The Tomb in has numerous Easter Eggs, including the Gold Armor, a piece of powerful gear you can get to survive waves of undead.
This equipment allows you to passively regenerate armor as you wear it, giving you continual defenses for your Operator. However, to gain this Gold Armor, you have to complete several tasks.
Before you start searching for the Gold Armor, try to collect a variety of good gear first. You'll need some powerful weapons and buffs to overcome the challenges tied to the Gold Armor, especially as more waves of undead begin to spawn.
Try getting some Mod Augments or Field Upgrades in Zombies first, then start looking for the steps you need to complete. The Gold Armor is rewarded for completing two different Blood Rituals unlocked on The Tomb map.
To start these rituals, you have to at least unlock a hidden area of the map called The Dark Aether Nexus, a void-like location that mirrors The Tomb.