The Index is an Arena-style mission type added in The Index Preview update, which rolled out an initial version of the gamemode. Headed by Nef Anyo and hosted by Cephalon Sark, it is the equivalent of Rathuum with the exception that the rewards are based around betting credits and getting bonus if your team wins.
The Index is unique as unfilled player slots will be filled with Tenno Specters, who use their abilities and engage enemies to collect points. To win, players must collect points dropped by defeated opponents by touching them, which will hover around the player in a similar manner to Health Conversion. They can then go to the enemy goal and touch it to score a point and teleport back to their own spawn, or they can continue to collect and stack points at the potential for bonus points, but at greater risk of losing them all when killed.
The Brokers
<tabber> |-|Anyo Corp =
|-|The Loan Reclamation Division =
|-|Zenith Galactical =