Soul Archer is a very old bow master and Morro's right-hand man, and a major antagonist in Season 5: Possession of LEGO Ninjago: Masters of Spinjitzu.
When the spirits of Anacondrai Generals freed the Cursed Realm, Morro also got out. And then Morro possessed the Lloyd Garmadon, brought the other Ghost Warriors and began to look the Realm Crystal which can release the Preeminent, the scourge which stops only when all the Sixteen Realms is damnable. Morro found the Realm Crystal, invited the all Ghost Warriors and began to release the Preeminent. But when Nya harnessed the full potential of her own Elemental Power, she creates a huge tidal wave and embed the Preeminent to Endless Sea. And therefore, it was the end of the Morro, the Ghost Warriors, the Preeminent and the Cursed Realm.