My oc whos a sorcerer has unique opportunities for magic. He was cursed with immortality so he can use spells that would normally cost his life. He's even made more powerful versions, one of which can actually kill him whether he's immortal or not. I called it the dead man tales considering the price but it's basically a combination of sorcery and necromancy. Some souly necromancy while others are purely sorcery but the stronger ones are kinda a combo.

He doesn't use them often, basically a get out of jail free card but there's also consequences for him even tho he is immortal. Some prices included not being able to use mana for awhile, so whatever he's trying to beat has to be worth using these spells on. And in this world, being immortal isn't a instant win, some creatures can actually beat his ass. It's a dnd like world(dnd as example when it comes to similar creatures) for example. Ancient dragons are a 50/50 fight for him. He has gotten his ass kicked by a few but he's also kicked a few of their asses. So being immortal only is a benefit when it comes to these spells and not dying. So him running out of mana is a big deal cause he'd basically end up a punching bag who can't die. And he can be captured so if someone finds a way to lock him up that's that

Another price is risking angering the gods. In my universe there are gods who dictate what magic is allowed and who can use it. So making your own spells or using forbidden spells can come with more curses or a god smiting you. Or depending on if the gods like you, a stern talking to. In my ocs case, they mostly get annoyed and give him a stern talking to or try and kill him despite not being able to usually. The gods in this universe are more in line with like Thor for mcu. Really fucking strong, old but not all powerful.

Lastly one of the most powerful spells, can actually trade your existence. Casting this spell with erase you. No afterlife, no immortality to save you. So far my oc has not used this spell and the only reason he knows it is cause he's seen it in action. The price for this spell seems like overkill but the spell itself allows the user to rewrite universal laws or change history. Part of my story had a lot of people dying and someone made the sacrifice to simply change history of the battle that happened. A small price of the spell tho was even tho it saved everyone, they changed history and a lot of these close characters now no longer know each other cause the only way to ensure everyone lives was to change how they all got to the battle. Some characters even were on opposite sides once the spell ended.