On Level 3 (Forest Fortress) you have the chance to get the Light Rune, as explained in various cheats. The Light Rune, when equipped, will slowly heal your character at the cost of 1 mana per second. It is a literal lifesaver because there are many areas in the game where you can heal yourself undisturbed.
What ISN'T explained is how exactly to obtain the Rune. There are two Witches of the Green on this stage. One by the upper middle of the map, near the Light Circle. And the other on the lowest part of the map, past the Water circle.
The way to get the Rune is not immediately obvious. You must first have the first Witch (the one on the upper side of the map) upgrade your Ice Ward spell to Level 3. To do this you might need to visit her several times depending on what level your Ice Ward is already at. The first Witch can and will eventually upgrade you to Level 3 of this spell. Until your Ice Ward is Level 3 the second Witch, on the lowest part of the map, will NOT know to give you the Rune. You may need to travel back and forth between the two witches in order to get both the spell upgrades, and the Rune.
Save the game when near a mushroom ring. Quit, then reload the saved game to restore your health.
Light rune:- Chapter 3, a witch and her sister will give you the rune and a spell.
Fire rune:- Chapter 4, Defeat the Beguiler and his clown to get the rune.
Water rune:- Chapter 8, reunite the lost brothers to get the rune.
Dark rune:- Chapter 10, reunite the two children with their mother to get the rune.
To get a type of magic that can kill anyone just get a red cape and have the strongest fire attack, then press Y,Y,B,black,white,A,A,X if you do this right you will hear a loud yell.