In nice graphical terms - it tries to make a flower around the hero, top/bottom, then left/right then diagonals. If one of these is blocked you can be pretty sure the monster will spawn in the other one.
Also, I always wanted to get a bit in-depth on it so thanks for giving me the opportunity
Here goes textwall:
This glyph is very different than Wheytwut in a way that makes it theoretically the most powerful or impactful glyph in the game
It crates an enormous efficency advantage, so large in fact that it's hard or even impossible to capitalize on in a way that would actually break anything. Just think - if you find it early, you pretty much start the run with most of the popcorn teleported to the entrance.
Normaly, building up a popcorn bowl actually costs you blackspace for exploration and popcorn can be in your way, stuck behind threats you can't fight, popcorn you want to kill early for piety can be hard to find while you run into popcorn you don't want to find. Wonnafyt does away with all of this and blows a big hole in the regular approach to a run, sets up all non-magic res popcorn to +1XP, declogs passageways, and sets you up for both level cannons and regen fighting at the same time. It also gets you piety for gods who like slowing things and can give you big advantages for the god juggling game:
If you thoroughly Wonnafyt a map early and then join Taurog, you can technicaly start the game with a lot of piety for killing magic users. You can also kill off the undead for one god, and then join Drac at an efficent rate. You can make sure you never have to sacrifice Mystera piety for exploration. Etc...
Then you have the debuffers - you'll always have curse removal fodder handy. If you keep it for a while, you'll be sure that other stuff you never want to fight is out of the passageways. It kills those annoying low level lifestealers. If you know that all the mosters of your level or lower are slowed, you can fight a blinker (a lifestealing blinker!) and it will never manage to escape into blackspace.
If you combine it with IMAWAL you'll always have a slowed popcorn to stone for +1 XP and +50% on your next kill (and curse removal).
And there's also at least one vicious map where it breaks a big part of the challenge like nothing else
The reason it's not too broken is that it creates such a huge efficency/blackspace advantage that you can't really cash in on it all most of the time. And you still have to explore to find altars, bosses, shops and powerups. But if you could prep it, that prep would allow you to play a variant of Desktop Dungeons quite a bit different from the usual setup. It's a bit like IMAWAL and LEMISI, in that it changes some fundamental rules (IMAWAL lets you play at a different XP progression, LEMISI gives you tons of info and with the right subdungeons can significantly increase the ammount of effective blackspace on the map). It's just, really, really front-loaded