Does 'Elf-Stone' require one of your Hero's to match the sphere of the Ally that you are putting into play?
The text says:
" Attach to the active location. Attached location gets +1 quest point.
Response: After attached location leaves play as an explored location, the first player puts 1 ally into play from his hand."
I'm assuming that is doesn't require a match and for example; Damrod could be put into play from a Mono Lore deck.