Right at the start of Terra Maledicta, you will hear an audio dialogue instructing you to collect a page from the Tome of Rituals.
Now you just need to complete the portals in the east and the starting area to reach the shield. Once the new area is unlocked, you will see an enclosed Wonder Weapon called the Decimator Shield.
The audio dialogue tells the story of this Wonder Weapon and that you need to destroy crystals to free it. You are also told that you must gain Vercanna’s trust in order to destroy the crystals.
From the starting area, you will find a portal to the north that you need to complete to gain access to the campsite and the Speed Cola.
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Complete the objective and then return to the area to find the speaker stone. The stone is located at one of the tents opposite the perk fountain. Interact with it to receive a new audio dialogue.
Once this dialogue is finished, a portal will open directly in front of you. Enter the portal and complete a quest. Stand on the glowing rune circles and kill the zombies until they disappear. Once this quest is completed, you will be automatically teleported back to the starting area. A new audio dialogue will now tell you how the crystals can be destroyed.
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You simply need to shoot the golden crystals in the starting area. This will direct the energy back into the Wonder Weapon, but it will still be locked. Return to the Wonder Weapon to receive another dialogue.
The dialogue will inform you that you need to awaken the Wonder Weapon. You must now find another stone, which is located near Double Tap. Interact with the stone to proceed to the next step.
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The stone is located on the ground floor of the bazaar. After interacting with it, a new portal will appear.
The portal will teleport you to the Dark Aether. There, you will have an encounter with an ally of Kortifex. Now, you need to protect the marked areas on the map while simultaneously dealing damage to the enemy.
The three masks that cover the face are the weak points. So shoot at these to inflict damage. Once you defeat the enemy, you will be teleported back to the Wonder Weapon, and you will notice that you can now pick it up.
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NOTE: WHEN YOU PICK UP THE SHIELD, ONE OF YOUR TWO PRIMARY WEAPONS WILL BE REPLACED. IT IS RECOMMENDED TO CARRY THE SHIELD ALONG WITH A PUNCHED SHOTGUN.
After another dialogue, we are asked to go to a stone near the blue perk fountain.
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After interacting with the stone, another story dialogue follows, and then another portal opens. This portal teleports you back to the Dark Aether, where the page from the Tome of Rituals is anchored to the map by glowing energy rods. Activate the shock ability of the shield near the red orb-like anchors.
Destroying these anchors will take some time, as your shield has a cooldown of about 90 seconds after each shock. During this time, kill any zombies that stand in your way. When your shield is recharged, an audio cue will sound, and both eyes of the shield will begin to glow. Once all the anchors are destroyed, the page will float down to you.
After you pick it up, you will be automatically teleported back to the starting area, where you can enjoy a lot of loot.
Congratulations, you have completed the Easter Egg!