Halo Wars 2 players will need to collect all the skulls in order to unlock the Collecting A Dream Achievement. Here is a guide on where to find the items and the effects they can use in battle.

Find The Skulls

There are 15 skulls located in the main game and each has its own traits. Players can get the first one by destroying the main base in Ascension mission. It causes Marine grenades and Grunt mines to splatter paint. Collect all the Power Nodes in the A New Enemy mission to get the second one. This item makes Grunts explode into pieces.

Players will get the third if they don't let any prisoners die in the One Three Zero mission. This piece allows supplies to come in 25 percent earlier. Destroy a Banished base hidden on an island in the Ascension mission for the fourth. This item decreases unit training time by 50 percent although the final score will go down. Liberate all Lights Out prisoners to collect the fifth. It makes a newly trained unit lose a bit of their HP although final score goes up.

Destroy a Banished northern expansion base in the Cartographer to get the sixth. This rewards players by cutting Power recharge by half. Prevent the Spartan from completing mission From the Deep to get reward. The piece increases Spartan Slam damage but decreases final score.

Make sure that the Particle Cannon's health will not fall to 50 percent in the Hold the Line mission. In return, the skull will cause Grunts and Marines to explode if they are killed. The explosion can damage enemies near them but final score will also go down. Make sure that all barricades survive in Hold the Line to get another one. This item cuts the units' HP by half but increases the final score.

Keep the Scarab alive in The Foundry mission since this will cause Scarab and Locust beam weapons to shoot rainbows. Keep the Scarab's HP above 25 percent to get another one. Units will receive 50 percent more HP. Kill the three Brute Warlords in the Under the Dark mission. This will make the hero unit unleash a nuclear explosion if killed. Rescue the Bravo Base in the Halo mission to get a tank or infantry unit as a reward. Wipe out the Brute Warlord and their forces in The Last Stand mission to get cloaked units as reward. In the same mission, keep the Control Shield damage above 20 percent. The reward is the removal of all checkpoints and saves but final score will go up. There is also a guide on how to defeat opponents quickly here.