Spellbook of dig
|spellbook of |
|Base price||500 zm|
|Turns to read||30|
|Ink to write||25–49|
|Power cost||25 Pw|
|Equivalent||wand of digging|
2.03% of all randomly-generated spellbooks will be a spellbook of dig.
While sharing most of the same uses as the wand of digging, the spell is quite high-level and power-intensive for the utility it provides - especially when the more-common wand grants the same benefits and the ability to engrave Elbereth in exchange for limited charges per wand. For training matter spells to eventually cast the spell of polymorph, the knock and wizard lock spells are better due to their lower power cost and comparatively wider use cases. By the time you reach Gehennom, you should typically have a large supply of digging wands and can obtain more from minotaurs and other hostiles, so it is typically not worth learning at that point unless you need a forgettable spell for quick confusion.
The spell is almost guaranteed to be useless to Cavemen, especially considering the availability of wands of digging - even with the special spell bonus and a robe, Cavemen have the second-highest spellcasting penalty among all vanilla roles, which compounds the above already-existing issues with the spell.
The guaranteed spellbook of dig you can obtain from the Wizard of Yendor on the Plane of Earth is intended to be a backup in the event you have no other sources of digging—this is also the case for the accompanying minotaur and Elvenking, who provide the faster wand of digging and a chance for a pick-axe, respectively. Even so, you should still have plenty of your own wands at this point, along with a means of charging them if needed.
All spellbooks are introduced in NetHack 1.3d.
In xNetHack, the spell of dig is lowered to a level 3 spell. Both this and overall changes to the casting system make it much less unwieldy to cast, though the wand of digging may still be preferable in many scenarios.