Mana burn

Mana burn is loss of life for not using mana in your mana pool when a phase ends. For instance, you tap a Swamp to cast Dark Ritual which gives you File:Manab.gifFile:Manab.gifFile:Manab.gif which you use to cast Erg Raiders. If you can't use the remaining File:Manab.gif then you will take 1 damage from mana burn.

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In-world meaning

In storylines mana burn happens when a wizard holds mana and doesn't use it to cast the spell. Such a wizard can seriously suffer from it, be killed, or even be burned to ash if the amount of mana was too big. Some victims of mana burn can be also turned to the Fallen.