Runes are the second most important part of any deck, only slightly less important than the cards themselves. Runes can duplicate a wide variety of abilities that your cards might not otherwise have access to. Runes have 4 important parts to them.
Element - Determines which faction is affiliated with the rune.
Effect - Determines the ability that is activated by the rune.
Condition - What factors have to be present to activate the rune. If the factors no longer apply, due to things like reanimation, the rune will de-activate until the factors are present again.
Level - Determines the level of the ability. Max level for runes is 4, with the base level of each rune being 0.
Earth Runes - Wilderness Runes
Fire Runes - Hell Runes
Water Runes - Kingdom Runes
Wind Runes - Forest Runes