Mutators are predefined rules in the game that alter numerous things, sometimes making the game harder, sometimes easier and sometimes neither and just end up doing something stupid.

Mutators are set in the local save .prison file and are formatted like this:

Here is an example of how you would format using the Big Heads and Endless Winter mutators:

Here is a list of the mutators, they are in order of how they are displayed in-game but with their code-names. If the code-name is different to the friendly name then I have put the friendly name in brackets.

HighDanger (Danger Zone) - Maximum danger level, prisoners will fight more often.
SuperDrugs (The Good %$#!) - Prisoners will gain a random trait when they take drink or drugs.
AcidRain - Rain and snow will damage prisoners, does not work if weather is disabled.
MoreVolatilePrisoners - Gives around 50% of prisoners the "Volatile" trait.
ExtremelyNeedyPrisoners - Makes prisoners needs escalate quicker.
GangWarfare - All prisoners will be in a gang.
MassEscapes (Get Me Outta Here!) - Prisoners will constantly try digging tunnels.
MoreContraband - More smuggles, more thefts, just more contraband...
AllLegendary (The BIG House) - All prisoners are legendary and have a lot of traits.

SuperGuards - Guards are smarter, faster, stronger and more observant.
AllRepsRevealed - Reputations/traits will no longer be hidden.
NoViolentPrisoners - Prisoners will very, very rarely be violent (if at all).
NoTunnels - Prisoners will never try digging tunnels.
FastDeliveries- Trucks will not deliver things anymore, they will just appear.
NoClipStaff (Spectral Staff) - Staff will be able to walk through walls.
ReducedDirtBuildup - Dirt appears at roughly 50% the speed as normal.

NoRevealedReps (No Reputations Revealed) - You will not be able to see the reputation/traits of any prisoners.
FastWalking - Everyone walks at twice the speed as normal.
NoPausing - You will no longer be able to pause the game.
NoRelease - All prisoners are sentenced to life, they never get to leave.
FastRelease (Short Sentences) - Prisoners are only with you for a few weeks.
ContrabandDetectors - Metal detectors now detect all contraband. (Uses 2x the power!)
OldSchoolIntake - You get new prisoners everyday, regardless of intake rules or space.
SlowTime - Makes the clock tick slower.
SlowDeliveries - Every single item has to be delivered on a truck and manually placed by workman.

BigHeads - All prisoners get big heads...
EndlessWinter - Winter will never end, like the ice age! Does not work if weather is disabled.
IndestructableTrees (Nature Conservation Zone) - You cannot destroy trees.
BurnTheDead - Dead people cremate instantly, no more hearses or morgues.
NoContrabandLimits - All contraband can be smuggled in and imported...
WeirdReputations- Strange traits they didn't make it into the full release of the game.
PermanentDay - It's just... permanently day time.
PermanentNight - It's just... permanently night time.
SpreadingTrees - Trees spread and grow at a faster rate than normal.

This guide is mainly for personal reference as I am currently working on a mod and want to look back at things like this. I will be making more guides to share what I have learnt from looking at the game code and development documentation.

You can see the mods I currently have released here:
https://steamhost.cn/steamcommunity_com/id/switchmodo/myworkshopfiles/?appid=233450