Seven for the Dwarf Lords, in their halls of stone.
"Calenardhon".
Suddenly this map is 10x more exciting.
EDIT: Could it be the War of the Elves and Sauron? We've got the Ring poem, and the presence of old names like Calenardhon (assumed Gondorian but could be earlier) and Lindon (almost always Second Age). We've got a big obvious space to the right of 'Eriador', and no similar space to fit 'Arthedain' (if they were doing the Fall of Arnor). And it
would make a good story, in the Game of Thrones way: Celebrimbor delving into Forbidden Arts with Satanic help, Numenor, if not going full slaver yet, at least utterly disregarding the rights of the local peoples, Lindon forting up and refusing to let anyone in, and Annatar the Bright wandering around stirring up trouble...
(This was suggested to me by someone on another forum, but most of the detail is mine.)
hS