Halo Wars 2 skulls

The Skull section of the main menu in Halo Wars 2.

Skulls are game modifiers featured in Halo Wars 2. When unlocked and activated they can alter gameplay difficulty and add interesting features.

There are fifteen skulls in total and they are awarded for completing specific Primary Objectives, Optional Objectives, or unmarked tasks throughout all of the missions in the game's campaign with the exception of the game's prologue The Signal and the DLC campaigns Operation: SPEARBREAKER and Awakening the Nightmare.

List of skulls

Grunt Birthday Party

"Killed Grunts explode into a shower of confetti, bringing joy to the battlefield - if you're not a Grunt, that is."

Unlock requirement: Capture four of Decimus' Power Nodes on the level A New Enemy.
Notes: After building your base, four Power Nodes will be shown around the map, indicated by an energy bolt icon. Move your infantry units to each of the nodes to capture them. Make sure to do this before carrying on with the Primary Objective.

Paintball

"Marine grenades and Grunt mines splatter the environment with color (as well as deadly shrapnel). Time to paint the town!"

Unlock requirement: Destroy the Banished base on Ascension.
Notes: After building your base, begin building a large army of Hornets and Cyclopes. Once you're set, head north, beyond Capture Node B, and you will find the Banished base. Do not capture any of the Capture Nodes until after destroying the base (so you won't face any opposition later). It is best to set up quickly, before the Banished can make its first move to capture a Node.

Pain Train

"All player units train 50% faster."

Unlock requirement: Destroy the hidden facility's four structures on Ascension.
Notes: After building your base, take three or four Hornets and move them to the darkened island south of your base. Here, you will find a hidden Banished base with a few Infantry Units. Use your Hornets to destroy the enemies and the four structures of the base.

Bountiful Harvest

"Supplies from supply buildings arrive 25% faster."

Unlock requirement: Don't let any of the four prison squads die on One Three Zero.
Notes: During this mission, Alice will be required to rescue four squads of prisoners, the first half of which are Hellbringers and the second half of which are Warthog Units and Cyclopses. Try to keep the Hellbringers in the rear while you focus on controlling/moving Alice throughout the mission. Once your entire squadron reaches the comms building, move your Hellbringers and Warthogs behind the building. Now move Alice and one Cyclops into one of the two garrisons in front of the building and move the other two Cyclops into the other garrison. Hold out like this until extraction arrives, making sure none of the Cyclops or Units behind the building die. It is okay to lose a few units, but do not lose a whole squad.

Emperor

"All player powers recharge in half the time."

Unlock requirement: Destroy both minibases in the central chamber on The Cartographer.
Notes: After powering down and passing through the energy barrier, you may notice that in the northern end of the chamber, on both the eastern and western edges, are Banished minibases. Make sure to destroy both bases before moving on with the Primary Objective.

Pestilence

"All player units slowly lose health from the moment they're built."

Unlock requirement: Release all 10 UNSC Prisoners on Lights Out.
Notes: You will find your first set of prisoners just north of the mission start or after the reunion with Douglas-042. Then, after passing through the portal, you will need to head to the right-hand side of the valley to find three additional cells of prisoners. Make sure to rescue them before fighting Decimus.

Total Annihilation

"Spartan special ability slams create an even more powerful explosion upon landing."

Unlock requirement: Complete the entirety of From the Deep without Spartan Alice being downed.
Notes: The best method to employ for this task is to have Alice either hijack a Wraith on the beach or take control of the Scorpion tank on the beach (either works). Make sure Alice is your primary focus throughout the mission; heal her when needed and make sure she doesn't take the brunt of the enemy's attacks. When the Scarab shows up at the end of the mission, you should already have a sizable army of Anti-Tanks (Cyclops and Scorpions) to accompany Alice in taking it down quickly. It's better to have a Nightingale accompany Alice most of the time, to save resources from using Restoration Drones. In addition, you can also do it in conjunction with hijacking a Locust as part of the Bonus Objective and it has more range to allow Alice to build up veterancy without taking too many hits.

Sickness

"All player units have 50% fewer hit points."

Unlock requirement: Keep the barricades intact on Hold the Line.
Notes: In this mission, you will need to protect the western and eastern barricades; the former of which is just to the left of your base and the latter of which is a little southeast of your base. The best way to ensure they aren't overwhelmed and destroyed is to build one Anti-Infantry and one Anti-Vehicle turret at each barricade and then place at least three or four Hornets and one Nightingale just ahead of the barricade as the "first line of defense." It's recommended to try doing this on a low difficulty, as the enemy forces become increasingly difficult to keep at bay past the fifteen minute mark. Alternately, create a kill zone with mixed anti-tanks and infantries (Recommended group of Full Upgrade Marines, Cyclops, and Nightingales) for better efficiency. In addition, two siege turrets and two anti-air turrets should be built on the base for defense support.

Firestarter

"Grunts and Marines explode on death inflicting damage on enemy units."