There doesn't have to be a twist. Sometimes, magic is just magic. There are plenty of types of magic where the cost is just the stamina of the caster and nothing more.
[ He says this, but he also wants to deter her from the whole dark magic thing. Mostly because Mei is sweet and he's fond of her, so Satan would prefer if she doesn't pursue Alastor's brand of magic. ]
I don't use Alastor's type of magic other than to make pacts. But, you should probably take his word at face value when he tells you the terms of his magic or his deals. That being said, if you're still interested in magic for yourself or for your school, I'm still happy to volunteer my services for free. No strings attached.
no subject
[ He says this, but he also wants to deter her from the whole dark magic thing. Mostly because Mei is sweet and he's fond of her, so Satan would prefer if she doesn't pursue Alastor's brand of magic. ]
I don't use Alastor's type of magic other than to make pacts. But, you should probably take his word at face value when he tells you the terms of his magic or his deals. That being said, if you're still interested in magic for yourself or for your school, I'm still happy to volunteer my services for free. No strings attached.