Skills and Skulls

Grab a floating dead guy’s head once you slay enough specific enemies to unlock some wild gameplay enhancements!

Aside from the main objectives throughout the Campaign mode and the Black Box hidden on each map that unlocks much of the timeline, there are more secrets to discover: the infamous Halo Skulls. There are 15 of them, and each appears only when you complete each mission’s Kill objective; be sure to return to the Skull’s location before ending the mission. Every Skull you collect is revealed on the menu showing your previously completed missions.

These Skulls have specific gameplay enhancements, which can help (or hinder) your attempts at a perfect score and a Gold ranking for each Campaign mission. The following table shows what enhancements to the game each Skull enables. Check these out before deciding whether to attempt a mission with this Skull turned on. Naturally, Skulls 11 through 15 are the most useful, because they give to an in-game bonus ability as well as (not instead of) a percentage added to your Complete Score ranking.

Mission Number	Skull Name	% Added to Mission Complete Score	Description of Skull’s Ability
01	Look Daddy!	None	Grunts’ methane tank always explodes on death.
02	Grunt Birthday Party	None	Grunts explode into confetti.
03	Cowbell	None	Destruction physics magnification x2.
04	Wuv Woo	None	Scarabs shoot rainbow beams made of Pure Love.
05	Fog	+10 percent	No minimap.
06	Sickness	+10 percent	All player units explode into Flood units on death.
07	Rebel Sympathizer	+20 percent	Nonplayer units receive +25 percent more Hit Points.
08	Rebel Supporter	+20 percent	Nonplayer units inflict +50 percent more damage.
09	Rebel Leader	+20 percent	Nonplayer units start with extra Veterancy.
10	Catch	+20 percent	Nonplayer units recharge abilities in half the normal time.
11	Sugar Cookies	+50 percent	All player units have 50 percent more Hit Points.
12	Boomstick	+10 percent	Five percent chance any nonplayer unit blows up on death, with splash damage.
13	Pain Train	+25 percent	All player units train 50 percent faster.
14	Bountiful Harvest	+30 percent	Supplies arrive 25 percent more quickly.
15	Emperor	+50 percent	All player Leader Powers recharge in half the time.