The Index is "a list S.H.I.E.L.D. keeps of people and objects with powers," though there are in reality, according to Phillip Coulson, "not that many people on the Index". The size and scope of the Index are never clearly quantified, nor how reliable the organization as a whole considers the material to be. There are two types of people on the index. Those who were born with powers are called gifted. Those who gained them later in life are called enhanced.
According to Agent Coulson in "The Bridge", there are no authenticated psychics on the Index. However, in "End Of The Beginning", the team and their allies return to check out discounted alleged psychics in case one may be The Clairvoyant.
The Index causes a problem in Season 4 when a terrorist group called the Watchdogs (organization) gets their hands on it. Thus, instead of protecting those on the list, the Index endangered the life of many Inhumans with some getting killed.
- "Girl in the Flower Dress" (mentioned)
- "FZZT" (mentioned)
- "Repairs" (mentioned)
- "The Bridge" (mentioned)
- "End Of The Beginning" (mentioned)
- "Scars" (mentioned)
- Mike Peterson ENHANCED
- Chan Ho Yin ENHANCED (deceased)
- Donald Gill ENHANCED (deceased)
- Thomas Nash GIFTED (name removed and deceased)
- Karla Faye Gideon ENHANCED
- John Bruno ENHANCED
- Francis Noche ENHANCED
- David A. Angar ENHANCED
- Daisy Johnson GIFTED
- Elena Rodriguez GIFTED
- Carl Creel ENHANCED (name removed after believed death)
- James (Hellfire) GIFTED
- Joey Gutierrez GIFTED
- Lincoln Campbell GIFTED