In the Raging Mage Tower and the Yielothax Dimension if the latter is accessible. When the Rise of Devovorga event is active, they can also be found between Skull Pillars all over Tibia and in all lairs of the bosses related to this event. In addition, one is located in the Realm of Dreams. There's also one in the Halls of Hope. Four energy gates can be seen at Travora's platform, although they are unreachable.
A gate of pure, pulsing energy.