If you don't have the DLC already, it adds another opportunity to get blue and white titanite slabs - much more easily, in the case of the former. It also has some of the best boss fights ever omg
I do have the DLC, not finished it though, I was an IDIOT and attacked the mushroom lady in like the first room because my brain was all "Herp a derp, throw fire at everything"
It's ok she's just a redundant Oolacile sorcery vendor and she gives you like three healing items for beating Manus Thx a lot grandma