Kold Mirage is a Side Job in Cyberpunk 2077. It will randomly show up in your Side Jobs as you play through the game, giving you a set of mystery coordinates. Select the Side Job in your journal and follow the waypoint out to the dump. This general area will look pretty familiar, as it is where Dexter dumped your body earlier in the game.
When you arrive on the scene, you will notice Dexter’s corpse on the ground and will be able to pick up the Plan B Iconic Pistol, Dexter’s weapon. From there, move to the fridge behind him and open it up. In here you will find a not-so-living legend, Rache Bartmoss. Bartmoss was, at one point, the most wanted man in the world after he crashed out the old net.
It looks like his fate was a messy one, and he ended up in a fridge in the middle of a landfill. Johnny will appear, and you can talk to him for a while before he tells you to search the fridge. Doing so will yield an old cyberdeck, and Johnny recommends you visit Nix at the Afterlife who may be able to draw some information from it.
Take the cyberdeck to Nix and ask him to look at it, he won’t believe who it belongs to at first, but will eventually realize what he is holding. Nix will be interested and want to connect with the deck. If you have 10 Intelligence you can ask him if maybe there is something nasty on it, but he won’t change his mind, and you can still prompt him to go ahead.
Nix will connect with the deck, and after a while, his brain will start to fry. It is up to you to save him. If you look to the left and scan the wall you will see a circuit breaker you can interact with. This will cut all the power, saving Nix, but the deck will be fried.
The other way to save him is by connecting with the console right beside him. If you jack into it you will need to go through a number sequence puzzle and can save both him and the deck that way. There isn’t much of interest on the deck, and it doesn’t matter how well you do in the puzzle.
The good news is that Nix managed to pull some daemons from it, giving you some free Quickhacks you may not have had until now. This includes Reboot Optics, System Reset, Sonic Shock, Short Circuit, and Memory Wipe.