Scroll of light
The scroll of light generates a permanent field of light. A cursed scroll of light instead generates darkness.
This scroll is relatively useless. You could just use a wand of light, or carry a lamp. (With a lamp, you also have a method to switch it off!) Thus, this scroll is a good candidate for blanking. This is especially true should you be able to find and read a spellbook of light; it is among the simplest of spells, and once you can cast it, any scroll of light is obsolete.
In the spoiler scrl-343.txt, a scroll of light costs $50, weighs 5 (like any scroll), has relative probability 90, and requires about 8 magic marker charges. The radius of light (or dark, if scroll is cursed or you are confused) is 5. For a blessed scroll, the radius is 9.