It expands on the current Velen map, adding a lot of locations in the Eastern part. So far I think it's a good expansion, good difficulty, new enemies and items, the story seems good so far, only thing a bit lacking in what I've played so far is Cockle's acting skills in a certain plot line, though everyone else's is great. I'm a bit tired of him, anyway. Wish the Polish actor would join the English voice actor cast instead.
Tagora, it's just a random loot armor, so not great stats or anything, the real Witcher set of the expansion is the Viper School armor, a recolored Kaer Morhen armor with very high stats.