Aisenis

Overview
In the game, the NPC was called Aisenis, and he titled himself a "Travel Magician." However, at that time, he was using an elf's body. He would appear in random places around Firuman in a completely arbitrary manner.

No one knew how strong he actually was. The only thing that could be confirmed was that no one in Firuman could actually hurt him.

In the later parts of the game, when the Lord of the Abyss Nozama personally descended, and the player's party invaded the demon fortress, Aisenis went into the fortress afterwards. What happened was that Nozama completely ignored the fellow. Based on Nozama's character, him choosing to ignore Aisenis showed that he had no way to deal with him.

With strangers, Aisenis might seem threatening. However, once you got to know him, he would start to seem more and more like a child. His greatest pleasure was ostensibly watching exciting things happen, according to what he said. However, whether or not this was true or just an excuse, nobody knew.

He was famous for his line, "Don't mind me; I mean no harm. I'm purely curious."

Description
Most likely, he was from the Void, someone able to travel across dimensions. Anyway, it was without a doubt that he was strong, at least Legendary level.