This first portal was discovered when Elyon lured Will, Irma and Hay Lin into the gym of the Sheffield Institute on demand of Cedric.
Here the girls also performed as Guardians for the first time. They closed the portal, but the gym burned down.

The second portal was found in a dungeon covered behind a wall of the basement below Elyon's house. Again she lured them to it, and again they escaped. The Guardians used this portal the first time to find out what's behind it, resulting the capture of Taranee by Frost. A second use of it was after a call for help from Elyon to release her adoptive parents.

The girls never closed this portal, because it was the only known entry left to Meridian since the chart of Hay Lin got burned. Cornelia sealed it off against Interpol agents Medina and McTiennan by raising an indestructible wall.

The third one was accidently found when mrs. Rudolph real origin was uncovered. In the identity of Galgheita she fled back to Meridian. Later she returned to the institute after having a "vacation".

To release Taranee from her captivity this portal was found with the help of both the chart and the Heart of Kandrakar.
Striking is the fact that Irma drew a picture in her school diary which was found back on the exact spot of the portal.

The fifth portal was created by Cedric in the painting "Eternal Spring" made by Elias van Dahl, to lock this former artist on the court of Phobos in his own artwork. Its existence was felt by Cornelia.
After being captivated into the painting by Elyon the Guardians provoked Cedric to open the portal and escaped after defeating Frost.

This portal, located in "Ye Olde Bookshop", Cedric's bookstore, was meant to be used as a foothold for an invasion and the destruction of the Guardians. Cedric blew the whole plan by himself.

The seventh portal, located in a maintenance room of the subway got reversed after an earthquake caused by Cornelia and Elyon. The palace containing the fountain through which Cornelia entered Meridian became the Earthside entrance.

In a try to make the wall collapse Cedric convinced many Meridians to follow him to Earth. The timing was bad, because most of the Guardians already were in the stadium. Will also discovered allies were to be expected among the Meridian people.

A Meridian family got through this portal when a train passed over the tunnel. The oldest son Reseph frightfully ran off into Heatherfield.

Thanks to a token left by Vathek Hay Lin found a clue where the tenth portal should be. Will finally spotted it in the Love Tunnel in the amusement park.

The locations of the last two portals remain unknown, needless to say that they vanished forever with the other ones by the hand of the oracle when Elyon ascended the throne.