World fall (aka apocalypse/cataclysm) is a technique a Death Eater begins with in Slash'EM Extended. It can also be learned by a pokemon that has gained enough level-ups to reach experience level 18. The zyborg can randomly learn this technique on a level-up, and the binder will learn it if he advances his matter spells skill to expert.
Using this technique causes the player character to scream "EYGOORTS-TOGAAL, JEZEHH!" and kill all monsters on the current level whose level is lower than the technique's level, but it doesn't work against unique monsters and quest nemeses. This technique has a very long timeout; the actual number of turns after which it becomes reusable is random, but usually it takes at least 10000 turns to recharge.
Pet users should be careful with this technique, as it might kill the player's pet(s) as well, and it may kill other peaceful monsters on the level, too.