Having a spell like sands of aaru(that you can buy) that take 20% of hp and mana for 5% chance of inflicting 'bizarre' also the spell doesn't deal any damage.
Now what are the effects of 'bizarre'
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It cause class passives to not work properly.
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It reduce summon/follower ai and affects other classes key passive too.
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It can reflect your spells on you (just like confusion from pokemon). Though that wouldn't be that common.
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It'll mess with using consumable and spells like confusion too.
Proc rate could be reduced and having a spell that sacrifice both hp and mana could be cool.
but not ones with miss turn chance or something like Confused