Hear me out, Savathûn took the form of the Colonel to infiltrate the remaining Guardians bases during the Red War. Now, Savathûn is smart, she knew we would win, and through the Colonel, she could watch us rebuild, and see all of our weak points up close. Furthermore, with her close relationship to Cayde, she was also able to learn high level, sensitive vanguard intel, something that can be very useful when fighting us. Lastly, once she was done gathering information against us, she asked Riven to dispose of Cayde-6, who was than killed by Uldren, who was controlled by Riven. [i]Mic Drop[/i]