I'm a doctor, not a mechanic
The Stealth mutator does exactly what you would expect. It provides every player with the invisibility powerup making them tough to see. Be warned though - this mutator places a fairly hefty load on the PC so you might notice a drop in framerate - especially when there are a few players on the screen.
This mutator is particularly silly when combined with the Eavy Darkmatch 3 mutator.
- bool CheckReplacement(Actor (UT) Other, out byte bSuperRelevant)
- This function performs a couple of actions. The first is to remove all instances of the UT_Invisibility class from the level (the invisibility powerup). The second is to create a UT_Stealth inventory object and give it to the player. The inventory object is given a huge charge (9999999999) so it lasts forever in game terms.