A Portal is a building in Draconius Go that allows you entrance to the Rift of Arcana, a parallel dimension in the game.
Get within range of the portal and click on it and you will be able to enter the Rift of Arcana. You may exit the rift at any time by clicking the “leave rift” button displayed at the top of your screen.
Portals are not permanent like other buildings in the game. They spawn randomly throughout the world for a set amount of time and then disappear.