Aos Sí – Irish fae, or Aos Sí, are supernatural beings of Irish mythology.
The character's true name is Brian Boru, but he was raised as Steven Lafferty so that he could not be tricked by the Aos Sí into revealing his true name. When he was a little boy, he was snatched, and a changeling was left in his place. The reason for this was that the Queen of the Aos Sí wanted to protect the boy as she foresaw that his line would unite the country and protect the Aos Sí from a terrible war. This is referring to Brian Boru (c. 941–1014), who was the high king of Ireland who consolidated power over much of the island and defeated a coalition of Irish and Norse forces at the Battle of Clontarf in 1014, and would be remembered as a national hero who fought against Viking invasions and brought a degree of unity to the fragmented Irish kingdoms.
Here is an old school 2ed sheet
