Here is a spelltype from my world...

Mages mark exists in two versions.

most of the spells create a powerfull effect that in powerclass would be similare to level 10 spells
these spells should be level 3 or a little more.

All these spells have the added effect that they MARK their caster with a special pattern of magical energy...

This mark is the weakness of these powerspells...
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ceyleyons mask:
when this spell is casted it gives its caster the magemark.
the casters face transforms into a dragons for the rest of the day and the caster can breathe fire like a dragon, the fire is as strong as the fires that any wurm/elder dragon could produce.
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Abataks fireball:
A target is hit by a fireball (saves allowed)
that does (aD&D = d4*10 damage).
When this spell is casted the caster is magemarked... the magemark dissapears after d4 days.
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The second type of spells prey on the first ones.

Oshtuns fire:
a target is hit by a fireball for d8 damage, but if the target is magemarked it is dealt d8*10 damage instead.
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A weapon or item can be imbued/enchanted so it has additional powers that would normally not be in that items possession, an item so empowered will magemark its bearer/user.
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These spells are like a nemesis, the users of the first kind will be punnish by users of the second kind...

Users that magemark themselves should be 5% of the population and those preying on magemarks should be 15% of population.

Spells that detect magemarks can add to the conflict...

Wicked darkman...