Light Rune: In Chapter 3, a witch and her sister will give you the rune and a spell.

Fire Rune: In Chapter 4, Defeat the Beguiler and his clown to get the rune.

Water Rune: In Chapter 8, reunite the lost brothers to get the rune.

Dark Rune: In Chapter 10, reunite the two children with their mother to get the rune.