Illuminati is an Illuminati-based website on the Deep Web. Clicking the pupil in the center of the iconic Illuminiati eye or clicking in the bottom right corner have a chance of generating a key via a text file appearing on the desktop. It only opens after around 3 A.M.

It's also part of secret ending "Where Am I" achievement. Requiring to do following:

Spoiler Alert

Open website at 3:30 A.M., click center of triangle (the pupil). Hit "666" on keyboard and secret password will be revealed. It's "AllThatRain".

It should be used on URL hidden on developer's website (View source).

It will reveal that URL is: http://7dfe55e682bcdcdf31a22641aa6a49dc.ann