I hear a lot about the Nightingale Armor, but I'm not sure how many types there are. I know that there are the three basic tiers, but I've also heard about the "Snowy Nightingale Armor", so now I'm wondering if there are other types of it.
2 Answers
In the base game, there is only one type of the Nightingale armor, with its enchantment magnitude based on your character level.
The snowy version you have heard about are from mods.
Based on the Nightingale Armor wikia page, it looks like there are just three tiers of the Nightingale Armor. The first tier is for levels 1-18, the second for levels 19-31, then the highest tier is for level 32+.
It looks like the pieces you are given come enchanted, however, so that may be where your confusion lies, as the Nightingale Armor has an innate Frost Resistance enchantment. See this post.
This is one of the most desired sets of armor that people want an unenchanted version of. Unfortunately what you get during the Thieves Guild quest line is it.
