reachwater rock requires to different dragon claws emerald and ivory dragon claw its part of the quest forbidden legend
There is only one that has this feature and it's the one dealing with the "forbidden legend" quest. It takes two claws through several doors near the end of the quest.
On a side note I was hoping for a dungeon that took all of the claws and I was hoping that the thieves guild dungeon had the claw for the door actually in game even if you couldn't use it.
edit:deadblood01 beat me to it and is correct.