The sixth-edition annotator whose honest shrug about portals is the only guidance any crawler has on them.
Carl excused himself to the rest room, went into his personal space, and pulled up the portals chapter of The Dungeon Anarchist's Cookbook, hoping for something better than trial and error. What he found was a note added by Crawler Milk, sixth edition, and it is mostly an admission of defeat: portals are hard to understand, there seem to be dozens of types that all work in different ways, and none of it is consistent.
Milk's catalogue is short and hard-won. Some portals are like doors you never know are there. Some, like the entryways between floors, work on a touch. Some you have to put a hand through, and then you begin to feel yourself dragged; go slack and you get pulled in, though you can still break free. Some only work if you are big enough to fit, and some the size of a button will pitch you into a monster den. Teleport traps, Milk concludes, are the worst.
Carl had already proved the entry the hard way. He had fed a weighted test rope into an abyss-tuned portal, felt it go tight and then tingle, dropped it, and watched the whole thing vanish — nearly getting dragged along with it. Milk's note is why he stopped experimenting. He added a passage of his own on the different manufacturer brands of portals for whatever future crawler reads the twenty-fourth edition.
Never described — Milk exists only as a byline on a sixth-edition annotation, name unattached to species, class or fate.
A long-dead Cookbook contributor whose honest catalogue of portal behaviours is the closest thing crawlers have to portal theory.