Titanfall 2

Story related, cannot be missed.

Cooper's Logbook:

The Draconis is making a beeline for the full scale Fold Weapon, with the Ark on board. We're going after it using some commandeered IMC transports. These Widows are fast, but so is the Draconis. Sarah says it's not over yet - this fight's about to go airborne.

Pilot Helmets 3

Objectives:

1. Board the Draconis and secure the Ark.
   Watch the airborne battle take place. Eventually, you will get blown off your airship.
2. Take control of the Malta.
   Your mission will change to take control of the Malta airship.
3. Fastball over to Blackbird 6-4.
   Climb onto BT's hand and he will throw you over to Blackbird 6-4 to continue with your mission.
4. Board the Malta.
   The Blackbird 6-4 will take you as close to the Malta as it can, jump when you're close enough.
5. Clear all the broadside gun platforms.
   Eliminate all threats on the broadside gun platforms and kill all the IMC grunts on the gun platforms.
6. Rendezvous with The 6-4
   After eliminating all enemies on the broadside gun platforms; rendezvous with The 6-4.
7. Take control of the Malta's bridge.
   With Sarah's help, use her ship to wallrun to the other side of the Malta's airship to take control of the bridge.
8. Hack into the Malta's bridge controls.
   Now that you have control of the Malta's bridge, hack into the Malta's bridge console to disable the ship's guns.
9. Sheer the ship directly behind the Draconis.
   You have control of the Malta now, use your knife to steer ship directly behind the Draconis.
10. Board the Draconis and secure the Ark.
    You're reunited with BT, embark with him and head towards the Draconis.
11. Defeat Viper and his guards.
    You'll need to defeat Viper who is the fourth boss of the game and his guards in order to board the Draconis.
12. Disembark to Fastball.
    After the boss fight, disembark BT so he can fastball you again.
13. Fastball over to the Draconis.
    As BT is preparing to throw you, Viper reappears once again for one final assault.
14. Kill Viper.
    Kill Viper once and for all before he destroys BT, to do this you need to aim for Viper's cockpit and take the shot while BT is restraining him. Killing Viper will end Mission 8: The Ark (trophy unlocks here).
15. Board the Draconis and secure the Ark.
    With Viper defeated, continue on with your mission and BT open a hatch for you to drop below.
16. Secure the Ark.
    Follow BT through the ship and secure the Ark and the The Ark trophy will unlock.

Defeating Viper:

Viper pilots the Northstar Titan Loadout and he's considered the hardest boss fight in the game. Viper is capable of aerial maneuvering as he is always airborne throughout the entire fight. This makes it very difficult to target him or track where he's going sometimes. There are numerous ways to go about defeating Viper's Northstar Titan, but I personally recommend using the Expedition Titan Loadout. Do not use the Vortex Shield [] as it makes you an open target, instead I suggest you hide in the very back of the ship behind one of the gun platforms (I used the right side gun platform). You can use these for cover while you aim at Viper with your Machine Gun. Use the Multi-Target Missile System [] to take down Viper's shields and harm his Health Bar whenever possible!

It should be noted that Viper isn't alone as he comes with Scorch Titan guards. Take these Scorch Titans out immediately before they get too close to your location. I personally recommend using your own Scorch Titan Loadout to deal with the two Scorch Titans [use Firewall]. Once they have been dealt with, return your attention back onto Viper as you now have a checkpoint. Whenever you have Viper's shields depleted and you have a Titan Core. Try using the Burst Core or Laser Core (Ion Titan Loadout) to inflict extreme damage (you'll be vulnerable if you do this). If you need Titan Batteries, search the top of the ship's deck for Batteries to restore your Health Bar. Last of all, if Viper is going to use his Flight Core Ability; it's best to switch to the Ronin Titan Loadout and press for the Phase Dash. This will make you immune to the incoming Flight Core Ability. If you cannot use this ability, you'll have to shift to the left or right continuously using the Dash [] until the Flight Core Ability ends.