Halo Wars skulls

Skulls are objects that Ensemble Studios hid in levels in Halo Wars. When obtained and activated they can alter gameplay difficulty and add interesting features.

How to find them
Each level in Halo Wars has an optional objective where you are asked to kill a certain number of a certain unit type, such as killing 100 Grunts in the first mission, Alpha Base. Once this objective has been completed, the skull location will flash on the mini-map for a few seconds, so it's important to watch the map as you complete the objective. To simplify this, the objective will have a counter that pops up every time you kill a unit of the designated unit type. For example, the HUD will show "56/100 Grunts Killed"; when you have killed 100 Grunts for that objective, the skull will appear.

Look Daddy!
Level: Alpha Base

Special Objective: Kill 100 Grunts.

Location: On the embankment near the downed Banshee where last set of Marines are found.

Icon: A skull with a dummy.

Effect: When Grunts die, their Methane Tanks always shoot off.

Note: This is perhaps the hardest skull to obtain, since most times, a player kills only 95-98 Grunts before the end of the mission. Try using only Warthogs to splatter the Grunts before the A.I.s kill them. Also, while inside Alpha Base, do your best not to destroy the Spirit transports, as they drop additional Grunts.

Grunt Birthday Party
Level: Relic Approach

Special Objective: Kill 20 Jackals.

Location: At the south end of Alpha Base.

Icon: A skull marked with Grunt mask and pink party hat.

Effect: Grunts explode into confetti after being killed.

Cowbell
Level: Relic Interior

Special Objective: Kill 45 Hunters.

Location: In front of the main console, where Forge and Anders are initially pinned down.

Icon: A skull covered with a cow pattern (white skull with black splotches).

Effect: Destruction physics magnified.

Wuv Woo
Level: Arcadia City

Special Objective: Kill 50 Elites.

Location: Very eastern part of the map near statue of man holding book.

Icon: A purple skull marked with a pink lipstick kiss on its head.

Effect: Scarabs shoot a rainbow made of pure love and hearts.

Fog
Level: Arcadia Outskirts

Special Objective: Destroy 5 Wraiths.

Location: North west of the map, on top the highway near two buildings.

Icon: A light turquoise mist covering the skull.

Effect: No minimap, final score will increase.

Sickness
Level: Dome of Light

Special Objective: Destroy 50 Banshees.

Location: In the hangar just behind and to the right of the UNSC Base.

Icon: A green mist covering the skull.

Effect: All player units have 50% fewer hit points, final score will increase.

Rebel Sympathizer
Level: Scarab

Special Objective: Destroy 10 Type-30 Locusts.

Location: Next to the power node to the west of the Scarab.

Icon: A skull marked with a dark green fist on its forehead.

Effect: Non-player units get 25% more hit points, final score will increase.

Rebel Supporter
Level: Anders' Signal

Special Objective: Kill 750 Flood Infection Forms.

Location: On cliff edge beside a crevice in the northern part of the map.

Icon: Same as Rebel Sympathizer, only the fist emblem is red.

Effect: Non-player units do 50% more damage, final score will increase.

Rebel Leader
Level: The Flood

Special Objective: Kill 20 Flood Stalks.

Location: By the downed Pelican to the east of your starting base. You will need air units, as ground units can't get to the cliff the Skull is on.

Icon: Same as Rebel Supporter, only the forehead is flaming.

Effect: Non-player units start with extra veterancy, final score will increase.

Catch
Level: Shield World Special Objective: Kill 350 Swarms.

Location: On the island in the south east section of the map (you need air units to reach it).

Icon: A skull marked with two baseballs on each side.

Effect: All player units' abilities recharge in half the time, final score will decrease.

Sugar Cookies
Level: Cleansing Special Objective: Destroy 100 Sentinels.

Location: North east section of the ship in between both platforms, or, between the tail-fins of the ship.

Icon: Normal skull, only it looks like a skull-shaped cookie.

Effect: All player units have 50% more hitpoints, final score will decrease.

Boomstick
Level: Repairs

Special Objective: Destroy 12 Spirit Dropships.

Location: North east section of the ship above the central structure.

Icon: A skull with its cranium exploding.

Effect: There is a 5% chance that any non-player unit blows up upon death with explosive area of effect damage, final score will decrease.

Pain Train
Level: Beachhead

Special Objective: Kill 10 Flood Bomber Forms.

Location: In the starting area, near the Flood buildings (west of the starting area).

Icon: A skull that is completely crimson.

Effect: All player units train 50% faster, final score will decrease.

Bountiful Harvest
Level: Reactor

Special Objective: Destroy 20 Vampires.

Location: North-most part of the map near the second Covenant base.

Icon: Normal Skull, only different colored fruits are on each side of skull.

Effect: Supplies come in 25% faster, final score will decrease.

Emperor
Level: Escape

Special Objective: Destroy 3 Scarabs.

Location: North east of the map near a hot water spring and a Flood base.

Icon: A skull marked with a crown.

Effect: All player powers recharge in half the time, final score will decrease.

Trivia
The Wuv Woo skull is a reference/continuation of a recurring joke in two of Ensemble Studios' previous games. In Age of Mythology, entering the cheat code "wuv woo" spawns the Flying Purple Hippo unit, while in Age of Empires III the code "wuv woo vol.2" spawns the Flying Purple Tapir. Like Wuv Woo skull, both units have an exceedingly cutesy appearance.