Seal the Deal is the Main Quest and the associated achievement for the map Die Maschine in Call of Duty: Black Ops Cold War. It involves a Requiem Strike Force going to the site of Projekt Endstation, a Nazi weaponry and energy research program in Poland. Originally shuttered and deactivated by the Soviet Union due to Undead Nazis roaming the halls of the site, the site was reactivated by the KGB Special Operations Group Omega as part of Operatsiya Grobovshchik to help give the Soviets the technological edge within the Cold War. It requires players to close the rift that has been opened at the Projekt Endstation facility by the Omega Group.
Seal the Deal requires the Decompressive Isotopic Estrangement Machine alongside all four of the alternate ammo-types. While the NOVA-5 and Cryo-Emitter variants can be unlocked without the completion of any steps, both the Electrobolt and Thermophasic are locked behind the unlocking of the Der Wechsler terminal.
After the cyclotron has been reactivated and the Pack-a-Punch Machine has been brought from the Dark Aether, another rift will open to the dimension once again. Interacting with it will take the players into one of the Dark Aether variants of Die Maschine with parts of a device known as the Aetherscope. This device is split into three parts which have a random spawning pattern every match.
- The Antenna is located in the Yard.
- The Middle Section is located in the Crash Site.
- The Bottom Section is located in the Particle Accelerator.
When a part is obtained, a group of Plaguehounds will spawn near where the part is located. If all the parts are not obtained before the Dark Aether forces the players back into the standard map, the rift will reopen after sometime has passed.
With all three parts, the Aetherscope can be crafted on the unique crafting table on the bottom floor of the Particle Accelerator, behind the Pack-a-Punch Machine. Doing so and picking it up will cause Weaver to give the Strike Team their new orders directly from the Director of Requiem, to shut down the cyclotron permanently.
With the Aetherscope in hand, a new Dark Aether rift will have opened up within the Medical Bay. However, prior to interacting with it, Interact with the terminal to learn that it requires a password. Heading into the rift will now have the diary of the Director of Projekt Endstation, Ulrich Vogel placed on the table by the terminal. Picking this up will cause a "spectral reflection" anomaly of Vogel to appear on the bottom floor near to the sink. Interacting with the anomaly will materialize his figure and the second interaction will give his diary to him, allowing him to monologue an entry. During this, a being known as the Megaton Overlord or "Mayak" will start to spawn as long as any player is in the Dark Aether. When Vogel is done with his entry, he will dematerialize and a new anomaly will spawn, first in the Control Room between the right most Trials rewards output and lastly by the Aetherscope crafting table. Now with Vogel's completed diary, the Der Wechsler terminal can be unlocked.
The holding tank for Der Wechsler is online but lacks power to function. Somehow, the alternate capacitators of the Decompressive Isotopic Estrangement Machine are able to power the machine enough through a shot. If the players are facing the Speed Cola machine, the right leg of the container must be shot with the Electrobolt, and the left must be shot with the Cryo-Emitter. On the other side, the right leg must be shot with the NOVA-5, and the left shot with the Thermoplasmic. Doing so will continue the start-up sequence but another fault comes up, the Decontamination Agent is missing.
With the Decontamination Agent missing, a new rift opens up between the Medical Bay and Particle Accelerator. Entering will have an anomaly by where the Decontamination Agent should be, interacting with it will reveal the "spectral reflection" of two Soviet soldiers called Dmitriyev and Kalashnik stole the golden Decontamination Agent due to thinking Der Wechsler was just another Nazi gas chamber. After the convocation, all players will be pulled out of the Dark Aether and a Dark Aether Wrench will be placed near to where the anomaly was.
This Dark Aether Wrench can be utilized on the broken tank within the Yard a total of three times before a zombie pops the hatch open, unable to exit. This Zombie needs to be killed as an explosive Lethal needs to be thrown at the hatch to cause the tank to fire, knocking over a tree and dropping the Decontamination Agent into the map. Picking up the Agent will spawn more Plaguehounds as well as put the player whom picked up the Agent itself into a more vulnerable state as they are unable to fire or melee while holding the Agent. Returning the Decontamination Agent will cause Der Wechsler to finally cycle on and become ready to accept subjects.
With Der Wechsler accepting willing subjects, a split Megaton can be utilized due to their nature of being former Omega Group scientists. Leading both a Megaton Bomber and a Megaton Blaster under Der Wechsler will cause them to be sucked into the holding chamber until the other can be captured. When both are captured, the intercom system will inform the players that the decontamination process can start, which is done at the terminal. Doing so requires all players be in the Observation Room of the Medical Bay, as soon as the process is started, the Observation Room is locked down and all zombies on the map are killed while the split Megaton forms are decontaminated and remerged into each other, reforming them into the man known as Orlov. Orlov however will react violently and break containment, causing the Observation Room to unseal and Plaguehounds to spawn.
Now with Orlov missing and Der Wechsler broken, a final Dark Aether rift will open in the "Living Room" with the anomaly in the Dark Aether located by the 1911 wallbuy. It's of Orlov musing to a photo of his wife and child about how he hopes that the reactivation of cyclotron will not change the world. After the muse, players will be forced out of the Dark Aether and the photograph will be by where the anomaly was. However, grabbing it will cause all the players to be forced to the cyclotron with a now more passive Orlov.
Orlov will denounce Omega Group and ally himself with Requiem to permanently shut down the cyclotron. During this, Orlov will start to shut down three systems of the cyclotron while Mayak, Megaton Bombers, Megaton Blasters, Plaguehounds, Zombies and Heavy Zombies all spawn to hamper the progress of both players and Orlov. Only Zombies and Heavy Zombies will interrupt Orlov while the rest will focus only on the players.
Upon the completion of the third system, Orlov will tell the Strike Team to leave and he will finish the job. Weaver will call in an Exfil as pillars of blue energy burst from the ground around the map, closing off sections of the map. Going through these deal 25 damage per tick while going through the center will instantly down the player. The Exfil is in the standard location and has the standard 1:30 timer but a lower count of zombies and Raptor-1 will be landed and waiting for pick up.
Getting on the exfil chopper will award 5,000 XP on first completion for the "Evil Unleashed" Dark Ops challenge and play a unique ending cutscene. With the achievement being awarded after the end of the cutscene.