Skulls are the first currency in the game. The other three are Diamonds, Orbs and Bloodstones.
How to get skulls
Bunch of Skulls
Three Skull icons appear for every building the player destroys. The amount of skulls the player receives for every icon depends on the level of the building that is destroyed. Extra skulls are acquired by clicking on villagers after destroying a building.
If the player is able to defeat the boss at the end of every fifth level, several skull icons appear, netting a more significant amount of skulls.
Player can purchase some skulls instant at Diamond Deal for 5 diamonds.
The amount of skulls each skull icon is worth can be increased by using items, shards, skills or scrolls.
Skulls as currency
Skulls are used as currency to buy upgrades for Bob the Necromancer or the monsters.
The player will lose all the skulls currently in his or her possession if they go through a time portal. Don't hesitate to use a time portal, however, because it makes the player stronger by repairing any Broken Orbs one may have acquired.