If you're racking your brains because you don't remember him in the anime, stop now. Ling is a manga-only character from a series of plots exclusive to the comic. That said, I'll try to leave this first part of his profile as low on spoilers as possible, but that's pretty hard to do. So just in case, SPOILERS TO THE MANGA AHEAD.

Ling -with both of the Xing groups, actually- was introduced on chapter 32, right after Greed's interesting death and during the Elric brothers' second visit to Rush Valley. It all started with Al picking up a fainted man on the floor in a humorous way. The brothers invited him to lunch (which really wasn't such a good idea afterwards), and he tried to bond with them. He told them he came from the Xing empire and crossed the big desert, passing by the Xerxes ruins. The Elrics seemed interested in the Eastern branch of alchemy, rentanjutsu, but unfortunately Ling isn't a practicer. He, however, stated he traveled this far to find the Philosopher's Stone and the way of immortality. Uneasy, Ed denied knowing anything about it. Ling didn't buy it and snapped his fingers; at the moment, two masked ninja-like bodyguards under his command assaulted the brothers.

The bodyguards were defeated and captured, but Ling managed to take them back, flee, and charge a huge tab on Ed on the restaurant. But it wasn't the end of the nightmare for Ed, as he found Ling, hours later, having tea at Atelier Garfiel automail mechanics shop with Winry's boss. He couldn't shake Ling off, as neither Al, or Winry, or Garfiel seemed to mind the Xinguese around. The brothers even had to remake the younger bodyguard's mask and bring them to Central City on train. In the trip, we found out Ling is only 15 years old, his family is important, and the bodyguards (Lan Fan/RanFan and Fu/Who)'s family served his for generations. On the station they all get separated, and Ling is put in jail for being an illegal alien. Later on he's rescued by Barry the Chopper, along with Maria Ross.

The jail incident made him meet Roy's subordinates and work with them -or offer his bodyguards' services- in several ocassions, which included meeting with homunculi such as Gluttony and Envy. Still, he went back to the brothers after knowing about Al's nature from Barry. He and Lan Fan (Fu was busy on a mission for most of the plot) stayed for a while on a hotel with Al and Winry, discussing several things. One of the revelations was the fact Ling is the twelfth son of the emperor, therefore one of the imperial princes, and he wished to find the way of immortality to please his father and become the heir, for it's important for the Yao clan's fate.

<< More about his plot, with even fatter spoilers, coming soon >>