Details here (http://boards.cityofheroes.com/showthread.php?t=208051). Rules and stuff are similar to those of the first challenge.
The theme is: "I challenge you all to write an arc for levels 5 to 10 with a story about a known hero or villain who loses their powers." I think it's a pretty good idea overall, not just the theme, but the level range -- I haven't seen too many low-level arcs, and they are a good thing to show to newbies in a "See, this is MA, it's fun!" way.
I'm going with an "all powerful heroes/villains temporarily lose their powers*" story myself, if only for the extra amusement of watching the Freedom Phalanx having to employ rookie heroes to save the world. Plus a low-level arc gives me an excuse to have Family bosses with Pinstripe's lines. :p
-- Z.
* may or may not be a complete power nullification. Void where prohibited. Do Not Taunt Happy Fun Ball.