The Vanguard Soldier is a NPC ally you can find during the mission Agree to rescue captured soldier from Borea (CoH and CoV, levels 35 - 50). He is the missing soldier you're looking for. He will be found fighting a Chief Soldier. Once free, he will follow you and will attack any Rikti in his aggro range. The Vanguard Soldier is a Pet class with the correspondent amount of hit points for his level.