This guide is written by request to give players insight as to how to access all six of the hidden levels. THERE ARE SPOILERS AHEAD.

Seven Portals: Bright Cruicible
Within the Seven Portals hub there are 3 silver keys, one in each Guardian. There are six silver doors that unlock bonus rooms on the same hub. Three of these six bonus rooms hold face switches, and generally less powerups than the others. You must access all of these rooms and hit all three switches to open the hidden portal which can then be found on the Seven Portals map.


Shadow Wood: Sacred Grove
Once you have recovered the castle key in Hipostyle go back to the Shadow Wood hub. There is one castle door on Darkmere, Caves of Circe, and Wastelands that will lead to puzzle rooms. Once all three have been solved a portal will open on the Shadow Wood hub.


Heresiarch's Seminary: Deathwind Chapel
On each of the chapel maps on the Heresiarch's Seminary hub you will find hidden arena rooms, usually behind some broken glass. Completing all three of these will activate the star gate on the main map that will lead to the hidden level.



Castle of Grief: Desolate Garden
Within the Castle of Grief hub you can find five books, one on each level (including one on the Castle of Grief map). These are very hard to find and are required to unlock the hidden level. In order to obtain the books you must first obtain four silver keys that are all located on the Castle of Grief map. You will notice that there are six doors on the walls of the castle. These doors open according to where the hour hand is pointing on the clock.

On Castle of Grief; once cleared hug the southern wall inside the keep until you find a secret passage that you lead you outside the eastern castle walls, this will lead you to a book.
On Forsaken Outpost; be on the lookout for a group of glass window panes on the other side of a small lava river. Behind one of them you will find the location of a book.
On Gibbet; In the northern most part of Gibbet after passing an orb tower there will be a T intersection. Taking the left passage will lead through a series of traps and number puzzle. Solving this will lead you to a book.
On Dungeons; You will find a room that holds many small prisons that open according to several number switches. Every prison room contains a floor switch, if everyone of these is activated then a passage will open in the southern most part of Dungeons. Within this area you will find a book and an important switch that will raise the water level on Effluvium.
On Effluvium; after raising the water level four times in total (1 at the start, 2 in the maze, and 1 from Dungeons), a passage will become available in the eastern part of the maze, this will lead to a book.
Take each book you collect to the library in Gibbet and insert them into the empty bookshelf to access the hidden level.


Necropolis: Vivarium
Rejoice! This one is easy to get to. At the very start of the level you must travel through a dark room maze to proceed. Instead of going up, travel right and south until you can't move anymore, then move left to find the hidden portal to Vivarium. Once you are there, the trick to finding the true treasure of Vivarium is to allow yourself to be hit by the slowest moving projectile.