User blog comment:Twilight Despair 5/Hell Trial Theories/@comment-5619706-20130330041257

There appears to be a pattern on the trials so my guess is that the third will be based on it.

The first one is to kill a hellhound (a collector of sorts of souls damned to hell).

The second one is freeing an innocent soul from hell.

The first one prevents the collection of a soul to hell by killing the collector, the second one frees a soul mistakenly sent to hell.

So the third could probably be purifying a tormented soul, something like preventing the transformation of a soul to a demon, or maybe even restoring a demon to its previous state/life. And what better target to purify other than Crowley himself (so he could maybe join the Team next season and help close Heaven as a motivation for the broken King of Hell), or maybe Meg, if they really haven't killed her yet.