Halo Wars 2

In order to unlock this achievement, you will need to complete all seven objectives (four Optional and three Bonus) and earn a gold medal on Legendary in the first mission of the DLC, "Gatecrashers." Unfortunately, you must do this all on one playthrough of the mission.

With this in mind, please see below for the mission's Par Time and Optional/Bonus Objectives.

Par Time

• 45 minutes

Optional Objectives

• Rescue India Company's captured Wolverines
• Find and defend India Company's Nightingale
• Kill both Goliaths [0/2]
• Activate all Banished holo-projectors

Bonus Objectives

• Eliminate Controller Sentinels [0/8]
• Lure Sentinels near Banished buildings to destroy them [0/5]
• Use Holo Decoy to distract Controller Sentinel [0/10]

For additional notes, please continue reading below.

Additional Tips

• Try to complete the mission within 2-3 minutes of the Par Time; the Par Time bonus at the end is important
• Save often throughout the mission and reload if you are losing too many units; the less deaths you have, the higher your combat bonus will be at the end
• Ignore the Phoenix Logs, they are not important
• Focus on building/upgrading Hornets and Nightingales units throughout the entire mission
• At the end of the mission, do not touch the Retriever Sentinel while the "swarm" is protecting it, otherwise you will lose too many units and damage your combat bonus

For an in-depth walkthrough of this mission, please refer to multi-step guide below, courtesy of Segendary Ty. All credit for this walkthrough goes to him. Please note that the walkthrough begins after the first teleporter. Directional references will be made assuming you do not rotate the map after the first teleporter.

1. After being teleported, retreat to the mini-base slightly northeast and destroy it. This will allow the Controller Sentinel to destroy the Banished base you ignored, earning [4/5] Banished bases destroyed for the second Bonus objective.
2. Once the Banished base is destroyed, build a mini-base and double back to the Controller Sentinel. Use a Holo Decoy to distract/destory it, then build an HQ.
3. Build three Supply Pads and two Generators at the HQ. Build an Armory at the mini-base. Start building Turrets at the entrance of your main HQ.
4. Move the ODST unit to capture the Power Node slightly northwest of Capture Point B, then have them return to the HQ.
5. Begin using your Leader Points. Unlock Restoration Field and Scatter Bomb (I and II) and later, when you have enough Points, unlock the Grizzly Battalion.
6. Upgrade your HQ, then begin upgrading/building your buildings in this fashion:
   • Upgrade Generators
   • Upgrade Supply Pads
   • Upgrade Turrets to Anti-Vehicle
   • Upgrade "Advanced Logistics" at the Armory
   • Upgrade "Fortify Base" at the mini-base
   • Upgrade your main HQ to Level 2
   • Build an extra Generator and then build an Air Pad at the HQ
   • Upgrade Air Units
   • Upgrade "Reinforcements" at the mini-base
7. Build 2 Nightingales and 8 Hornets, then upgrade Air Units once more
8. Move the ODST unit to Capture Point C. Once it's captured, call in a Holo Decoy to stay in the area and distract the Controller Sentinel, and then return your ODST unit to the HQ. Do not destroy the Controller Sentinel just yet.
9. With your ODST Unit, Hornets, and Nightingales, move to Capture Point B. Once it's captured, use a Holo Decoy to distract the Controller Sentinel, and then destroy it. Before moving onwards, allow your Nightingales to heal your units, and make a few additional upgrades:
   • Upgrade Air Units
   • Upgrade your main HQ to Level 3
   • Upgrade "Advanced Logistics," "Fortify Base," and "Reinforcements" at the mini-base's Armory
   • Upgrade "Wingmen" at the Air Base
10. Move your army northeast. At this time, your main HQ should be heavily fortified with four Anti-Vehicle turrets so you should not have to worry about keeping any additional units around the HQ. Your army at this time should consist of your ODST unit, 16-20 Hornets, and 4-6 Nightingales.
    • If you have the Leader Point(s) available, unlock the Grizzly Battalion as soon as you can. If you have the population room, summon the Grizzlies into your army.
11. Continue northeast and attack the Banished Base. Focus on the Shield Generator and Turrets first, then kill the Goliath that's stampeding around. Once the base is destroyed, begin building your own base and move your ODST unit further east to active a holo-projector.
    • After destroying this base, you will most likely get the distress call to rescue India Company's Nightingale. If this happens, round up your Hornets and Nightingales only and head over to the distress beacon on the other side of the map. Once you get to India Company's nightingale, you will need to defend it for around 30-60 seconds before the objective is marked as complete.
12. For this new base, upgrade it to Level 2 and then Level 3. As for the buildings, make one Garage and six upgraded Supply Pads. Build one Anti-Vehicle Turret and one Anti-Infantry at the entrance of the HQ. Build one Anti-Vehicle and one Anti-Air Turret at the backside of the HQ. At this time, finish upgrading everything at the mini-base's Armory, and then destroy the Armory and build an upgraded Supply Pad. You should have enough energy at this time, so destroy the Generators at your first HQ, too, and replace them with upgraded Supply Pads.
13. At this point, you should be sitting at around 28-31 minutes. Leave the Grizzly tanks at the most recently built HQ. Move your ODST unit and Hornets/Nightingales back to Capture Point A. Once taken, use a Holo Decoy to distract and destroy the Controller Sentinel.
14. Using these same units, move up to Capture Point C and use another Holo Decoy on the Controller Sentinel here before destroying it. Now slowly make your way north towards Capture Point D.
15. While you are taking Capture Point D, the second Goliath will attack; kill the Goliath to complete the Optional objective. Once Capture Point D is taken, quickly retreat near Capture Point C. The Controller Sentinel will destroy a Banished mini-base on its way to Point D, completing the second Bonus objective. Use a Holo Decoy to distract the Sentinel and then destroy it.
16. Take your army to the northwest corner of the map to find and activate the third and final holo-projector.
17. Now move your army back across the map to take Capture Point E. Make use of Holo Decoys to distract the Controller Sentinel and complete the third Bonus objective.
18. If, at any point, your Hornets begin to die, replace them with fully upgraded Wolverines from the Garage of your second HQ.
19. Once all five Capture Points have been taken and you are at a maximum population, rescue India Company's Wolverines in the center of the map.
20. Take your army to the final terminal near the light bridge and activate it. This will trigger the Retriever Sentinel to spawn.
21. Use all the firepower you have to take down the Sentinel's shields. At 75% health, it will summon a Sentinel swarm. Fall back at this time, and do not attack or get near the Retriever Sentinel until the swarm dissipates and the ODSTs give the "OK" to move in.
    • The Retriever Sentinel will do this again at 50% and 25% health. Once the third swarm flies away, finish off the Sentinel to complete the mission

If everything went according to plan, you should have finished the mission between 43-48 minutes with all seven objectives completed. Even without any score-increasing skulls activated, you should a comfortable score for the gold medal score.

All in all, with every Optional and Bonus objective checked off, and a gold medal obtained on a Legendary playthrough, the achievement will unlock.