Ivory King DLC - boss question

[Djoan Nefarius]

Greeting, how do i access of one of the 3 DLC bosses?
I defeated Ava and Burnt Ivory King, i found a tower with some coffins in it and a locked door, where do i find a key to said door?

[TrueArchery]

If you go from the 1st to the 2nd bonfire, right in front of the drop to the 2nd bonfire, don't jump down, but go straight forwards until you see a stone door with 4 torches. Light the torches, the door opens automatically and the key is in that area guarded by several retainers and a flexile sentry.

[JimPappa]

Right before the 2nd bonfire, there's path leading to a stone door and 4 sconces in front of it. Light those sconces and explore the cave inside.

[Djoan Nefarius]

Ok thx, gotta say - this forum is very active and thus very handy.
I guess people are warming up playing DS2 before the 3rd one comes out.