Sie Kensou is one of the young disciples of Chin Gentsai who wields psychic powers - dubbed by SNK as Psycho Powers. Both he and Athena are trained by Chin to prepare for "the worst case scenario of oncoming evil" and use the tournaments as a method of training for such an event. Plans go awry when Kensou loses his powers in The King of Fighters '99 yet saves Athena with a previously unknown latent energy.
It is later revealed to be the Dragon Spirit (龍の気, Ryuu no ki), a power he somehow shares with younger teammate, Bao. He regains his powers and masters this newer power in The King of Fighters XI, much to the satisfaction of former NESTS member, Ron. The deeper meaning of the Dragon Spirit's importance has yet to be revealed. It's probable that the Dragon Spirit is a reference to Kensou's ability to morph into a dragon from Psycho Soldier.
(Source: SNK Wiki)
