Faust is a passive generator program which generates +2 PWR per turn, but also has a 20% chance of triggering a random daemon each turn. Faust can be chosen as a starting program, but cannot be acquired otherwise.
The Daemon Code achievement is awarded for completing the game with Faust and Brimstone as your starting programs.
Faust's +2 PWR per turn compares favourably to most other generators; but the downside of triggering random daemons is quite severe. Normally, the more harmful daemons such as Labyrinth and Validate should be managed carefully or avoided entirely, but this is impossible with Faust because it gives no advance warning of which daemon will be triggered, or when. The downside is less severe when playing with the Contingency Plan DLC, which dilutes the pool with more less-harmful daemons, but still bad enough that Faust is generally not considered to be a good program.
Because of the chance of daemon reversal, Faust triggers daemons on average every 5.55 turns, or every 6.25 turns when paired with Brimstone. However, Brimstone's high PWR cost somewhat negates Faust's high PWR generation. Faust's downside can also be mitigated by Bless which reduces the duration of some daemons, or by Central's Antiviral Proxy augment which generates +5 PWR each time a daemon is triggered. Together, Faust and Central generate on average +3 PWR per turn.
Faust generates enough PWR per turn to sustain Archive Prism's Holo Projection Mesh indefinitely.