I just played Skyrim again and used the Steam Workshop to mostly install cosmetic mods like HD textures, realistic water, the Ridgeview housing, and a mod that promises to add more enemies to the world.
So far, these mods have not been damaging to the lore of the game, but yesterday, after finishing "Mercer" and obtaining the skeleton key, I was on my way to the Pilgrim's Path when I made a stop at Whiterun and found an NPC in Nightingale armor selling "epic" items like these:
The funny thing is that the merchant had voice acting. As I continued to the Pilgrim's Path, I also found a follower named "Steve" full equipped in Daedric armor that I could hire for free.
Is this some mod that screwed up my game?