The Vanguard Adept is a NPC ally you can find during the mission Defend Portal Corporation from Serpent Drummer (CoH and CoV, levels 40 - 50). There are two of them. These soldiers have been captured by the Rikti during their assault and need to be rescued. Once free, they will follow you and will attack any Rikti in their aggro range. During my mission, the Vanguard Adepts had Pet class with the correspondant ammount of hit points for their level. Rescuing them are mission objectives, and a wave of Rikti will attack each of them once you have saved them.