If you are carrying a magic marker and are reasonably well-traveled in the Dungeons of Doom, the scroll of blank paper is possibly the most useful scroll in Nethack or Slash'em, since it allows you to write your own scroll. Prerequisites for making your very own scroll:
- Scroll of blank paper
- Magic marker
- Knowledge of the scroll you wish to create
It's the third one that's most problematic. You can't write a scroll of genocide if you don't know what is written on one, and to do so you must have previously identified (by means of the identify spell, sitting on an opulent throne and being granted an insight, using a scroll of identify, or actually reading the scroll) a specimen of the scroll you want to make. Magic markers are sometimes found lying around in chests or large boxes in the dungeon, on the floor, carried by monsters that pick up things (gnomes, for example), or in hardware shops and general stores.
Scrolls of blank paper are sometimes found lying around or carried by monsters, but there are ways to make them yourself if you already have some scrolls you don't need (an obvious use for that scroll of fire, scroll of destroy armor and scroll of earth you're lugging around). You can zap them with a wand of cancellation, dip them in a potion of water (dipping in holy water yields a blessed scroll of blank paper, unholy water a cursed one) or a fountain, as well as falling into a pool of water. Furthermore, paper golems fall apart when killed, turning into a number of scrolls of blank paper, some of which are usually cursed. The cursed/uncursed/blessed status of a scroll created using a scroll of blank paper is a combination of the the cursed/uncursed/blessed status of the magic marker and the paper used to make it.