Portal Gem

Portal Gems are used in the main campaign story of Dungeon Keeper 2. The player must obtain all 20 of them to gain access to the overworld. Every time you beat a level, you obtain a Portal Gem.
The Portal Gems were devised and created by King Reginald's Wizards from Harmonia's Royal College of Wizards. They prevent evil creatures from entering the overworld, whilst still permitting the heroes access to the underworld. The twenty Portal Gems were assigned to each of the twenty fiefdoms of Harmonia's custodians. Since then, many lesser Keepers have been driven away from Harmonia. In Dungeon Keeper 2, Horny teams up with the player in order to conquer Harmonia for the gems, so he can access the overworld. Each gem's power is tied to its realm's guardian's life force, meaning that they must die before Horny can arrive to seize it; however, he has been working on a method of utilising the energy of the captured gems for himself.
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