Forgotten Door

The Forgotten Door was an ancient sealed passage that Dalin and Company discovered in Riverthrone while making their escape from the arena through the sewers. The door was of the finest ancient Dwarven construction, fitting perfectly into it's frame with no visible seems, and invisible to all but the most observant. Underneath a layer of moss, the door featured hieroglyphics depicting death and destruction wrought by a large humanoid wearing a black helm, as well as a scene of the helmed figure being defeated by ancient men, elves, and the first Dwarven kings. The final panel depicted the body being sealed in a catacomb. There was also 3 diamond shaped holes below an inscription in Ancient Dwarvish:

Only one who hath proven their worth in the halls of Elves, Men, and Dwarves may enter here.

After finding the door, Dalin carved a message into the stone:

Dalin and Company discovered this seal and will attempt to uncover its meaning, beware all who pass here.