In Rich Burlew's D&D-themed webcomic Order of the Stick, the villains have as a pet/servant/ally a powerful monster that has stayed constantly hidden in magical darkness for the entirety of the comic. Exactly what type of monster it is has been a subject of a great deal of speculation among readers of the comic.
Whenever the species, origin, or nature of this "Monster in the Darkness" is finally revealed within the comic, this market will resolve to the most precisely accurate description of it, to the best of my ability to judge.
This means, for example, that if the MitD turns out to be a phrenic half-crystal dragon tarrasque, then the prediction "a phrenic half-crystal dragon tarrasque" would take priority over the prediction "a tarrasque with some kind of template to give it teleportation powers." But if it turns out to be a paragon pseudonatural chimeric giant giant potted plant, then "A potted plant with a poopload of templates" would still win if no more precise prediction were entered.
For neutrality purposes, I will not be betting in this market.
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@JiSK Glabzrezus have the ability to grant wishes (but not to themselves), and are big and scary. It's the simplest answer.
@MargaretHouston The sole word of god is that it's something Rich "did not make up", so we can rule this one out.
@JosephNoonan Sure, that's fair. Given statements from the author, though, I think it's almost certain we'll get more information than that at some point.
@EzraSchott Excellent question. In a perfect world, the market would magically close/resolve as soon as the reveal happens, and it wouldn't be an issue, but I doubt that's likely to happen. I'll probably just do my best to not resolve to any responses that were initially added after the reveal is posted, as far as I can determine that based on timestamps.
(I doubt this market is going to be active enough for it to be an issue anyway.)