This rune causes 10 damage every 9 seconds for a period of time. How long the effect will last depends upon your level and magic level.
This rune is most effective when used as the first attack against a strong creature, causing them to burn while being attacked. It's used mostly in PVP combat to keep the enemy from logging out or fleeing to a Protection Zone. Note that the caster is not able to logout while target burns, too.