Shrines

There are four elements of magic. Each element has it's own shrine.
There is also a 5th element which shrine is hidden from sight. The 5th element balances all the other elements.

In order to reach the end of the game, you need to enter Castle Nex and in order to enter, you will need to create 4 elemental essences. An elemental essence is created by collecting 4 powergems and placing them on the altar inside the shrine. The shrine will fuse the powergems together into the essence belonging to that shrine.
The shrine of fire will create the essence of fire, the shrine of earth will create the essence of earth, and so forth.

As said there are 4 shrines and a hidden 5th.
You only need the four shrines to create the essences needed to enter Castle Nex.

The shrine of fire is located in Twigroot Forest
The shrine of earth is located in Keelbreach Bog
The shrine of water is located in Sleet Island
The shrine of air is located in Hamlet of Stormbreach
The (hidden) shrine of balance is located in the River Tunnels.