Magic Channeling

You can increase your spell damage or healing power by an extra runic power each time you double the required casting speed. If the casting speed is 2 and you channel casting the spell for a casting speed of 4, you can add a second runic power to the spell. If you channel that spell to a casting speed of 6 you get to add yet another runic power to it. You can only channel a spell up to 4 times.