Wei

 Master Wei was a well-known Waterbending master from the Northern Water Tribe.

History
When Master Wei met Aang, he consulted him about the abduction of a young Waterbender and hunter named Hiryu, who had been kidnapped by anti-bending machines created by Lian. Master Wei sent Aang to scour the North Pole in order to find clues that may help determine the identity of Hiryu's abductors, or the cause of the Waterbender's abrupt disappearance. After Zuko raided the village, Master Wei informed Aang that Hiryu was probably dead.

Trivia

 * Master Wei is similar in appearance to Master Pakku. Strangely enough, Pakku is also a Waterbending master in the Northern Water Tribe.
 * Master Wei is one of the few Water Tribe characters who doesn't have a "k" or an "aw" sound in his name. Others characters who lack the characteristic Water Tribe sounds include Nini and Ummi.