How do you get skulls in Orcs must die 2?

Question

At the end of each game you get from 1 to 5 skulls. But what exactly decides how many you get? I'm only able to get 3 it seems, even though no orcs get through my defenses.

How do you get skulls in Orcs must die 2?

Answer 1

To expand on mordi2k's answer a bit:

Basic map skulls can be earned only once, and are earned 2 per map in Apprentice and 5 per map in War Mage difficulty. These skulls are shared between difficulties, earning them in one of the difficulties automatically gives them on the other one.

At the same time, repeating a map in Nightmare difficulty (unlocked after completing the game) allows players to earn 5 more skulls per map that are not shared with the lower difficulties.

Of the 5 skulls earnable in the maps, 4 are based on how many Rift Points are left when the level is complete, and the remaining one is earned if the level is complete within the level's par time.

Bonus skulls

Here is the list of bonus skulls you can earn at the end of a level:

• Victory, 1 skull: Win a level.
• Perfect Victory, 1 skull: Don't lose any Rift Point.
• Perfect Buddy Victory, 1 skull: Don't lose any Rift Point in co-op game.
• Untouchable, 2 skulls: Never be hit. Vampiric Gauntlets don't count against this bonus.
• New High Killstreak, 2 skulls: Make a killstreak higher than any precedent on that character.
• New High Score, 1 skull: Beat your preceding scores on an already played map.
• Skulls Picked up, 1 skull each: 1 for each skull picked up during the mission (dropped by enemies), it is not shared with the other player. (Question on what causes skulls to drop)
• 100 Career Kills, 1 skull: Kill 100 enemies.
• 200 Career Kills, 1 skull: Kill 200 enemies.
• 300 Career Kills, 1 skull: Kill 300 enemies.
• 400 Career Kills, 1 skull: Kill 400 enemies.
• 500 Career Kills, 1 skull: Kill 500 enemies.
• 1000 Career Kills, 1 skull: Kill 1000 enemies.
• 5000 Career Kills, 5 skulls: Kill 5000 enemies.
• 10000 Career Kills, 5 skulls: Kill 10000 enemies.
• 20000 Career Kills, 5 skulls: Kill 20000 enemies.
• 500 More Career Kills, 1 skull: Kill 500 more enemies. Earned only when the others Career Kills milestones aren't met.
• 1000 More Career Kills, 2 skulls: Kill 1000 more enemies. Earned only when the others - Career Kills milestones aren't met.

All information obtained from the Orcs Must Die Wikia

Answer 2

If you look at the stats page after the level is done, you'll see that you get;

• Max 4 skulls from not losing any rift points. (You will lose rift points by either dying, or letting enemies get through the rift.)
• 1 skull for completing the level within par time, which varies depending on the level.

You can also gain extra skulls from reaching certain milestones, or getting them as loot from enemies (note that these skulls do not count against the 5 skull scoring system).

Answer 3

adding to the answer of mordi2k, you can set the timer on in the options and that will pretty much tell you how much time left for each stage so don't idle during breaks that let you place traps before pressing "G" to unleash the horde.