The Doomsday Heist Act 3, or 'The Doomsday Scenario' consists of 5 setup missions, each with their own unique prep missions and the grand finale.
The initial setup cost is GTA$ 120,000 but the payout for completing the heist on normal is GTA$ 1,800,000 and on hard GTA$ 2,250,000. So your return is well worth the investment.
Prep 1(a) - Marked Cash
For the first prep mission you will be tasked with collecting a duffel bag filled with cash, which will be used to rescue Agent 14. Selecting a chopper or equivalent mode of transportation will help you ditch the cops and complete the mission much more easily.
Upon collecting the duffel bag you will receive a 4-star wanted level. Simply jump in your aircraft and head back to the facility with cash in tow, or call Lester to remove the wanted level.
Prep 1(b) - Recon
For the next prep mission you will be performing reconnaissance so head over to the Pacific Allied Shipyard and document the entire area. You will need to take pictures of the required locations with your phone and send it to Lester. Once you have finished, vacate the premises to complete the mission.
Setup 1 - Rescue Agent 14
For this setup mission you will want full snacks, armor, and ammunition. You will also want to consider bringing an armored vehicle such as the Armored Kuruma to make life a little easier for you and your team.
Clearing the first wave of enemies with your Kuruma puts some legs on your supplies and all but guarantees you will have enough provisions to last for the duration of the mission.
Go to the shipyard and take out the surrounding enemies, then head inside the warehouse through the main northern entrance.
If you did bring an armored vehicle, stay inside of it while taking out the enemies to preserve your snacks and armor. Once you have cleared the area, make your way to Agent 14 to trigger a cut scene.
After you gain control of your character, immediately take cover behind the crate in front of you and prepare to fight the AI Juggernauts using whatever heavy artillery you brought. The 3 AI Juggernauts are invisible so switch to your now accessible thermal vision mode and eliminate the new threat. Pro Tip: Have one teammate direct their fire while the other lobs grenades or whatever method of disposal you prefer.
They are armed with mini-guns, which deal high damage so make sure to prioritize cover while you are engaged in combat with them. After you have disposed of the Juggernauts run through the door on your left, make your way to the end of the warehouse, and prepare to fight four more Juggernauts. Flank them while they are preoccupied with your teammate but be sure to take cover as they will switch targets if you are too exposed.
After you eliminate the Juggernauts, you will now need to deal with the newly arrived helicopters. Make your way back to your vehicle, taking out the new enemies and protecting Agent 14 as you make your way to the indicated area.
In the next area, two more Juggernauts will spawn. Take them out, get back in your vehicle and advance. Pro Tip: Flanking them while they are pre occupied with one of your teammates drawing their fire is a surefire way to save a headache, some supplies, and munitions.
Once you enter the final area, you will face more soldiers and two more Juggernauts. Take them out and continue to clear the area. Pro Tip: If you and your teammate focus fire on a single AI Juggernaut you can drop them quicker. Headshots and grenades work great here.
After you have secured the area, jump into the Akula helicopters and escort Agent 14 to the drop off location to finish the mission. Make sure to fly below the radar, keeping low to the ground to avoid being tracked.
Prep 2 - Chernobog
For the second prep mission you will need to head over to a Merryweather Camp and steal a Chernobog. It is being guarded by a heavily armed group of mercenaries so you will want to consider bringing an armored and or weaponized vehicle for this job. After you have taken out the mercs, the driver of the Chernobog will jump out and run away. Jump in and bug out.
While returning the Chernobog to the facility, more enemies will be in pursuit. However, their efforts are inconsequential; ignore them and head straight back to drop off the Chernobog and complete the mission.
Setup 2 - Escort ULP
This mission is fairly difficult as you will need to keep the ULP Agent alive while fending off swaths of enemies using outdated and clunky weaponry; AKA the Chernobog. Full provisions are recommended but not required as the machinery will be doing most of the heavy lifting for you..albeit semi manually.
To get this party started, head to the Paleto Bay Construction Yard and take out the security detail. Using an armored vehicle for the first sequence of this mission will save your supplies but it is not necessary as you will be protected by the Chernobog for the most difficult part of this setup mission.
Eliminate the enemies, then depending on how many teammates you have, you can proceed forward with two strategies in mind. If you have two players max, both of you need to be in the Chernobog because only the passenger can use the missile system (required to be stationary while firing) while the other drives and enables/disables the guided missile system. If you have 3 or more players, the extra player(s) can jump in the Ramp Buggy to stay ahead of the Chernobog while clearing a path so the other team can focus on providing air support for the ULP Agent.
Make sure to keep up with ULP as he can get swarmed and chipped away at fairly easily. If the agent's health bar runs out, it's game over. Ignore the choppers that are focused on you. The Chernobog can take the heat.
Keep progressing forward keeping the helicopters off of the agent and eventually the enemies will fall back and you will automatically complete the mission.
Prep 3 - Flight Path
For this prep mission you will need to travel to the designated location and identify a target. Upon arriving you will see the mark leave the area. Tail behind him and once he is isolated, shoot him using a stealthy weapon.
After you have killed the target, retrieve his briefcase and return it to the facility. Mission complete.
Setup 3 - Barrage
This setup mission is a step up in difficulty but if you are stocked up on armor and snacks it won't be so bad. An armored vehicle is recommended but not required. You will be tasked with taking down a Cargobob transporting a Barrage.
Go to Observatory and take down the Cargobob using the Heavy Sniper Rifle with Incendiary Rounds. Aim for the rotors to expedite this task. Once you have felled the transport chopper, head to the wreckage and collect the Barrage. Pro Tip: If you only have 2 players, make sure Team 2 gets on the top mounted machine gun as it has a 360 degree field of view as opposed to its secondary machine on the back which has a restricted range of motion.
After you and your team are in the Barrage head to the Sandy Shores Airfield and take out the plane that is taking off on the runway. Next, kill everybody else. Once you have cleared the area, you will need to drop off the newly acquired vehicle to the designated location. Pro Tip: Anticipate the waves of enemies and have your inventory open as you drive so you can spam snacks when your health gets too low.
Continue down the road and head to the drop off location. Mission complete.
Prep 4 - Test Site Intel
For this prep mission you will need to first retrieve information regarding the status of the Khanjali tank's location. You have two main strategies here, either go in guns blazing and deal with the consequences of alerting the authorities or stay in stealth and make your way into the house.
Just take out the guards that are in your way of the lockbox. Inside you will find a laptop that contains the location of the test site for the Khanjali. Once you have collected the laptop head back to the facility to drop it off and complete the mission.
Setup 4 - Khanjali
This setup mission is easy enough if you are a decent shot with the Khanjali. You can further simplify the job by selecting an Armored Kuruma as your personal vehicle to insure you and your team take minimal damage while acquiring the tank.
Go to the aircraft scrapyard and clear the perimeter. Next, take out the equipment marked on your mini-map. Grenades or any explosive device will work here. Once you have destroyed the indicated targets you will be able to access the Khanjali.
Once you enter the tank you will need to head straight to the drop off point. You can expect to encounter enemy helicopters, tanks, and soldiers. The driver will have access to the railgun which makes short work of the enemy choppers and the tanks while the other teammates have the option of either a mounted machine gun or a grenade launcher.
As you approach the drop off location, the enemies will give up and you will have free rein over roads for the home stretch. Pro Tip: Do NOT railgun the Agents waiting to receive you at the drop off site...unless you want to redo the last sequence for funsies...
Prep 5 - Onboard Computer
For this prep mission you are tasked with shooting down a prototype Hydra. We recommend using a Buzzard or comparable weaponized aircraft. Note: You will want to have plenty of rebreathers on deck as you will need to fetch the module you are after by diving underwater once you down the Hydra.
Get into the vehicle of you choice and catch up to the Hydra. As you approach you will lose any homing capabilities you have and you will need to aim manually.
Once you've sent the Hydra to Davy Jones' locker you will need to dive down and recover the module from the cockpit of the Hydra. After you collect the module, an enemy chopper will appear and a timer will start counting down, so stay low and fast while making your way back to shore. Team 2 can down the chopper if they are feeling helpful. Pro Tip: If you happen to have the Kosatka Submarine, the Avisa mini-sub is a great niche tool to assist with the recovery of the module.
Once you are back on dry land, head back to the facility to drop off the module and complete the mission.
Setup 5 - Air Defenses
For the fifth and final setup mission you and your team will be piloting a Volatol over Mount Chilliad to take out the SAM turrets that are scattered along the general area.
Go to the Sandy Shores Airfield and all teammates get into the Volatol. The pilot will be doing the brunt of the work if not all for this mission as they will need to maneuver the plane and be in control of the bombing. We found that the enemy choppers and aircraft were not a threat to the Volatol. Simply focusing on the SAM's was more than sufficient.
You are tasked with destroying 12 SAM turrets while navigating enemy helicopters and aircraft. Pro Tip: fly close to the turrets and glide over while engaging the carpet bombing mode to make short work of the SAM turrets. Ignore all enemy helicopters and fly the enemy jets into the mountain by juking up as they attempt to close in on you. Action packed.
After you have taken out all 12 SAM turrets, return to the Sandy Shores Airfield to complete this mission.
Act 3 Finale - The Doomsday Scenario
This finale is pretty brutal so make sure to have maximum provisions and supplies before you start.
Head to Grapeseed and jump into either the Khanjali or the Barrage. Unless you're DMX...we recommend the Khanjali. It is slower than the Barrage, but it's, well, a tank. It is worth mentioning you will receive an extra GTA$ 100,000 if you choose the Barrage and only an extra GTA$ 50,000 if you choose the Khanjali.
Make your way to the tunnel entrance. Upon entering you will need to fight your way through.
Once you are at the end of the tunnel four Juggernauts will spawn. Take them out using the rail gun. They are not invisible this time so you do not need any thermal gear to combat them. After you have destroyed the Juggernauts you will need to ditch the vehicle and proceed by foot. Continue forward, taking out everything along the way.
As you approach the doorway, you will encounter another Juggernaut. Take cover and clear the room, then continue forward. Once you reach an intersection you will be asked to split up and destroy the supply boxes in each hallway. As there is no timer yet, you can stick together or split up. The hallways are connected at a juncture later on anyways so you can double back easily if necessary or flank the apponenent if the opportunity presents itself.
Do not stand close to the supply boxes when you destroy them or you will die. A couple shots from your Special Carbine from a distance will get the job done.
After you clear all of the supply boxes in the hangar area you will come across some supply boxes in a hallway. Take cover behind them because there are two more Juggernauts waiting for you. Take them out and move forward carefully as there will be a couple more Juggernauts waiting for you ahead.
Keep heading to the control center, take out the enemies, and trigger the cut scene. You will next need to make your way to four different server locations and hack them. This is the most difficult section of the heist by a long shot as you will face an army of clones that infinitely respawn. You will need to provide cover fire for your teammate as they perform the hack. Note: Once you advance to the next area you will trigger a timer where you will have twenty minutes to hack four server terminals or face nuclear annihilation.
Proceed cautiously through the double doors, a small army of clones awaits you on the other side. After you take out the first six or so clones run through the doors and up the stairs to the right and make your way to the second floor. Clear a path through the clones and head straight to the server terminal to begin the first hacking sequence.
You have a short leash with the timer here so hustle to each server terminal and begin hacking immediately. You will not take damage while performing the hack but you will be vulnerable to fire after completing the mini-game as you will be exposed.
The hacking mini-game is straight forward enough. You need to break the blue colored nodes by shooting a laser through them while avoiding the red nodes. If the laser stays on a red node long enough it will shatter and you will lose a life. Lose two lives and the game resets.
After you successfully hack all four servers the clone army will stop respawning. Clear the room and make your way upstairs to the Orbital Cannon to take out the four mobile cloud servers. After you have destroyed the targets, go back downstairs and head to the Silo for the final showdown with Avon.
Expect heavy resistance along the way. Clear the enemies carefully as you move forward. Once you reach the end of the tunnel a cut scene will play. Avon escapes using a jet pack so you and your teammate(s) will follow suit, jumping into your own jet packs and chasing after him.
Use the homing missiles to take out any enemy helicopters that are obstructing you from locking onto Avon. He only takes a couple hits to down and the enemies will stop spawning once he is dead so focusing on him is the priority.
After you kill Avon, you will need to return the Jet Packs to the Observatory where you will trigger the final cut scene and complete the finale of the Doomsday Scenario. Congratulations!