Consumable: Vanguard Research Token
Proof of study done on behalf of Vanguard Research.
Obtained: You can obtain these in two different ways. The first way is to complete Challenges that are given to you daily. This will reward you with 3 tokens. The second and more efficient way to do this is to visit Ikora in the tower after beating the story and replay random story missions from her. This is only possible after beating the main story! Talk to Ikora and accept one of her purple-colored quests. Then use the machine to the right of her. This machine will allow you to replay a random Story Mission at 220 Power. Upon the completion of the Story Mission you will be rewarded with 3 tokens.
Usage: Redeem with Ikora in the Tower to increase Reputation. Handing 7 Vanguard Research Tokens will give you a legendary (purple) engram. You get access to Ikora after the story in the Tower.
This is where you find Ikora in The Tower to trade in the Vanguard Research Tokens: