Howling Halls sounds altogether like a prison. Actually, there do seem to be a vast variety of prisons in the Whoverse. Speculatively, there could have been some reason to imprison a number of these elemental shades, or perhaps a melange of elemental creatures for whatever reasons. The use of the definite article "a" instead of "the" seems to imply that there was more than one that may have wanted to escape, which could be interpreted as a supporting clue.
Also, sorry for adding this initially on the Howling Halls Talk page. I must have perused the new member reading material in a circumspect manner, as it took me some ten minutes to determine where to put speculation. Siirenias ☎ 17:11, June 21, 2013 (UTC)
The Howling Halls were mentioned in Love & Monsters, weren't they? I don't think we've heard of them before or since. As you say, the name sounds very much like a prison & the Doctor's use of the word "escaped" suggests the same. Certainly, neither term makes the place seem like a holiday resort.
It's a pity that "an Elemental Shade" from "the Howling Halls" was a throwaway line in one of the least popular episodes but maybe some writer will one day pick up on the idea & give us a story about them -- hopefully a rather better story than their origin. --2.101.59.47talk to me 22:26, June 21, 2013 (UTC)