Nytefall is the first Loyalty mission unlocked in the game, as it is available after completing the Matt’s Back story mission.
Matt has designed a training simulation and wants you to go through it with him. Meet up with Matt inside of the simulation and you’ll see that your powers are gone for the time being. He starts the training simulation and it turns out to be some NyteBlayde fanfiction, with you being attacked by a horde of zombies. Just keep killing them until no more come out, then head outside to meet up with NyteBlayde.
Get in the car and follow NyteBlayde until you stop and have to take out a bunch of enemies. Once you do, get back in the car and continue following NyteBlayde. When you get to the church, Zinyak chimes in and says he has rewritten the ending to Matt’s little story.
He turns NyteBlayde against you and you’ll have to fight him. He’s nothing more than an enemy with a few powers (Telekinesis, Super Jump and Blast), but you don’t have any powers of your own. So, just keep shooting at him and slowly whittle his health until he is finished. Although that’s all you have to do, the mission is prolonged a little bit so Matt gets some super powers.