Lyon *MAJOR ENDING SPOILERS*

[Tokuro]

Not only the rune of punishment suck the life of the user. Apparently all the true runes wannabes (like the Black Sword, Bright Shield and Twilight rune) have a power that is almost as great as a true rune, but sucks the user life. But hey everyone agreed that she die because she fought when she should not (and because that stupid prince didn't command her to stand back...)

[Milan Fiori]

Runes are physically draining, but they aren't life draining. Only the Rune of Punishment drains the life of the users. Of course the Soul Eater drains life from people close to the user, but that's different. But the other runes just leave you exhausted. Such as then Riou uses the rune in Tinto to escape, and then collapses in Tigermouth or whatever. It also appears the more insynch you are with your rune, the less draining it is. We know that even though they don't have their rune, master rune bearers like Sierra can control their rune from afar.
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Be awed by our prowess!