A player asked for a list of differences in challenge mode. I hadn't been maintaining one until now, but here we go: * Effective minimum monster difficulty is 1 higher than in normal mode, and maximium is 1.25 times as high. * Elemental resistances reduce damage to 1/3, rather than to 0. * HP regeneration is slower (for the player). * Sleep attacks put you to sleep for longer. * The chances of AD_DRST, AD_DRDX, and AD_DRCO attacks draining the corresponding attribute are higher. * The chance of a c attack starting the stoning process is higher. * The chance of an eel wrapping itself around you (to drown you) is higher. * Amulet stealing attacks are four times as likely to succeed. * Nurse dancing is less effective. * Gremlins are more likely to steal properties. * Stunning and slowing attacks are twice as likely to affect you. * Confusion and drain-energy attacks always succeed against you (if MC doesn't block them). * Death's touch works slightly differently. (NOTE TO SELF: maybe not as intended.) * Regaining lost levels (via potion of full healing or via prayer) works as in vanilla: you can only ever regain half of them (rounded up). In normal mode, you can regain all of them. * There's a score multiplier. * Killing anything disqualifies you from entering the quest at experience level 1, even if you don't gain a level from it. * Scrolls of identify will identify fewer objects on average. * A blessed scroll of charging will sometimes work as uncursed. * The minimum luck needed to be guaranteed a wish is higher. * Charged rings in starting inventory are more likely to be +1