Lava rune

Lava runes are runes crafted by combining Earth and Fire runes. This can be achieved by taking
 * pure essence, Earth runes and an Earth Talisman to the Fire altar or
 * pure essence, Fire runes and an Fire Talisman to the Earth altar.

These runes count as one of each type used to make it. Combinations have a 50% success rate and the talisman is consumed in the process. This is one of the combination runes released with the abyss update.

Lava Runes are used for the quest, Swan Song.