Wish magic was a high-level type of magic that only archmages and powerful existences could use. However, wish magic wasn't actually that rare at all in this world. Wish magic would often appear in stories, plays, myths, and so on… but would always be on the evil side, or end in a bad result.
Anyone who truly understood wish magic would never think about trying to rely on it.
A wish could become real? Haha, if something so wonderful really was true, then mages would have long since conquered the world already. Anyone who had used wish magic before would likely arrive at an identical conclusion—that they absolutely didn't want to ever use wish magic again.
The main reason for this was because the great majority of wish magic spells followed the principle of equivalent exchange. The more you paid, the more you could obtain.
"Don't be greedy."
