Scroll
Scrolls are single-use readable items represented by a bright-yellow ? in Omega 0.90.4. They can provide information, improve equipment, grant temporary powers, or radically alter a level, while cursed copies often reverse or spoil the expected benefit.
Every scroll weighs 5, has fragility 1, and belongs to the common rarity class.
Scroll types
| Scroll | Base value (Au) | Item level | Cursed name |
|---|---|---|---|
| Blank scroll | 5 | 0 | Antinomy! |
| Scroll of spells | 250 | 1 | Scroll of spell loss |
| Scroll of blessing | 400 | 2 | Scroll of cursing |
| Scroll of acquirement | 5,000 | 7 | Scroll of destruction |
| Scroll of enchantment | 200 | 2 | Scroll of disenchantment |
| Scroll of teleportation | 75 | 1 | Scroll of teleportation |
| Scroll of wishing | 10,000 | 10 | Scroll of wishing |
| Scroll of clairvoyance | 25 | 1 | Scroll of amnesia |
| Scroll of displacement | 50 | 2 | Scroll of vulnerability |
| Scroll of identification | 20 | 0 | Scroll of forgetfulness |
| Hint sheet | 10 | 0 | Hint sheet |
| Jane's guide to treasure | 50 | 2 | Jane's guide to treasure |
| Scroll of alertness | 50 | 1 | Scroll of drowsiness |
| Scroll of cosmic flux | 300 | 5 | Scroll of cosmic flux |
| Scroll of charging | 100 | 2 | Scroll of draining |
| Scroll of the warp | 100 | 3 | Scroll of the warp |
| Scroll of self-knowledge | 10 | 1 | Scroll of delusion |
| Scroll of law | 100 | 2 | Scroll of law |
| Scroll of heroism | 200 | 5 | Scroll of cowardliness |
| Scroll of true sight | 50 | 2 | Scroll of blindness |
| Scroll of dispelling | 250 | 3 | Scroll of self-dispelling |
| Scroll of summoning | 300 | 2 | Scroll of summoning |
| Scroll of light | 30 | 0 | Scroll of darkness |
| Scroll of deflection | 250 | 3 | Scroll of vulnerability |
The base value is the ordinary, uncursed scroll's value before identification and BUC adjustments. Pawn-shop stock is fully identified and an ordinary scroll's shelf price matches this value. When selling, the pawn shop offers half of the value it can recognize: unidentified scrolls are heavily discounted, partially identified scrolls receive a smaller discount, and cursed scrolls are refused.
Finding scrolls
Scrolls can appear among random treasure on dungeon floors and in monster inventories. The pawn shop can stock eligible scrolls, and a scroll of acquirement can produce either a random scroll or, when blessed, a chosen scroll. Some monsters also carry a particular scroll.
Random treasure does not give every scroll the same final chance. Each treasure source has a level. Floor treasure uses the area's difficulty, which ranges from 1 to 10; pawn-shop stock uses level 5; and random monster treasure uses the monster's level, which can include 0. A scroll below the source level always qualifies; a scroll at the same level qualifies about 67% of the time, one level higher qualifies about 34% of the time, and a scroll at least two levels higher qualifies about 1% of the time. When a candidate fails, the treasure is rolled again from all item classes, so the replacement is not necessarily another scroll. Randomly generated copies begin uncursed.
| Scroll level relative to source | Design qualification rate |
|---|---|
| Lower | 100% |
| Equal | about 67% |
| One level higher | about 34% |
| At least two levels higher | about 1% |
Final random-scroll design probabilities
The scroll pool contains four level-0 types, five level-1 types, eight level-2 types, three level-3 types, two level-5 types, one level-7 type, and one level-10 type. For each source level, the qualification rate for one scroll is divided by the qualification rates of all 24 types combined. The resulting figures are the chance that an accepted randomly generated scroll is one particular scroll of the listed item level. They include rejection and rerolling, use the game's intended equal-outcome random model, and are rounded to three decimal places. For example, at source level 1, each individual level-0 scroll accounts for about 9.862% of generated scrolls, while each individual level-7 or level-10 scroll accounts for about 0.099%.
| Scroll item level | Source 0 | Source 1 | Source 2 | Source 3 | Source 4 | Source 5 | Source 6 | Source 7 | Source 8 | Source 9 | Source 10 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 14.790% | 9.862% | 6.485% | 5.249% | 4.831% | 4.682% | 4.474% | 4.409% | 4.346% | 4.284% | 4.225% |
| 1 | 7.506% | 6.607% | 6.485% | 5.249% | 4.831% | 4.682% | 4.474% | 4.409% | 4.346% | 4.284% | 4.225% |
| 2 | 0.221% | 3.353% | 4.345% | 5.249% | 4.831% | 4.682% | 4.474% | 4.409% | 4.346% | 4.284% | 4.225% |
| 3 | 0.221% | 0.099% | 2.205% | 3.517% | 4.831% | 4.682% | 4.474% | 4.409% | 4.346% | 4.284% | 4.225% |
| 5 | 0.221% | 0.099% | 0.065% | 0.052% | 1.643% | 3.137% | 4.474% | 4.409% | 4.346% | 4.284% | 4.225% |
| 7 | 0.221% | 0.099% | 0.065% | 0.052% | 0.048% | 0.047% | 1.521% | 2.954% | 4.346% | 4.284% | 4.225% |
| 10 | 0.221% | 0.099% | 0.065% | 0.052% | 0.048% | 0.047% | 0.045% | 0.044% | 0.043% | 1.457% | 2.831% |
There is no single context-free percentage for one scroll among all random items. The final absolute percentage also depends on the levels of the other item classes and on which one-off items remain eligible. The table therefore reports the stable comparison a player can use: the design distribution among scrolls after the level filter has finished.
Unidentified inscriptions
At the start of a new game, the following pool of thirty inscriptions is shuffled. The 24 scroll types receive the first 24 shuffled names, leaving six unused in that game. An inscription learned in one game therefore cannot safely identify the same scroll in another. A scroll's cursed name appears only after its type has been identified.
| No. | Inscription | No. | Inscription |
|---|---|---|---|
| 1 | scroll-GRISTOGRUE | 16 | scroll-Aratron Samael |
| 2 | scroll-Kho Reck Tighp | 17 | scroll-De Wormiis Mysterius |
| 3 | scroll-E Z | 18 | scroll-Necronomicon |
| 4 | scroll-Kevitz | 19 | scroll-Pnakotic Manuscript |
| 5 | scroll-Arcanum Prime | 20 | scroll-Codex of Xalimar |
| 6 | scroll-NYARLATHOTEP | 21 | scroll-The Mabinogion |
| 7 | scroll-Gilthoniel | 22 | scroll-Ginseng Shiatsu |
| 8 | scroll-Zarathustra | 23 | scroll-Tome of Tromax |
| 9 | scroll-Ancient Lore | 24 | scroll-Book of the Dead |
| 10 | scroll-Eyes Only | 25 | scroll-The Flame Tongue |
| 11 | scroll-Ambogar Empheltz | 26 | scroll-Karst Khogar |
| 12 | scroll-Isengard | 27 | scroll-The Yellow Sign |
| 13 | scroll-Deosil Widdershins | 28 | scroll-The Kevillist Manifesto |
| 14 | scroll-Magister Paracelsus | 29 | scroll-Goshtar Script |
| 15 | scroll-Qlipphotic Summons | 30 | scroll-Pendragon Encryption |
Reading scrolls
Scrolls cannot be read while blind or afraid. Cancelling before choosing a scroll leaves it in the inventory. Once a scroll has been read, it is normally consumed even if a later target or text prompt is cancelled or rejected; exceptions and important targeting details are described on the individual page.
Blessed, uncursed, and cursed copies may have very different results. The BUC table on each individual page describes those outcomes from the reader's point of view.
Loss and destruction
Reading normally consumes one scroll. Cancelling before choosing a scroll is safe, but cancelling a later target or text prompt usually does not prevent consumption.
A scroll can also be lost in the following ways:
- The Destroy an item command can shatter a selected scroll.
- An acid trap can damage possessions unless the reader dodges the spray or has acid immunity. A normal fragility-1 scroll subjected to the general item-damage check shatters 14 times in 15.
- Entering the Abyss removes all possessions, including scrolls.
- A cursed scroll of acquirement can destroy a random possession. A scroll of blessing can disintegrate a sufficiently cursed target. Misusing the Orb of Earth can disintegrate all possessions.
A blessed scroll may resist the general item-damage check according to its item level, but this offers no protection to level-0 scrolls and is unreliable for low-level ones.
Strategy
Protecting scrolls
Acid immunity prevents an acid trap from damaging possessions, making it the most direct protection for carried scrolls. Avoid entering the Abyss with scrolls that must be retained. Blessing can improve the survival chance of higher-level scrolls, but it should not be treated as dependable protection for low-level copies.
Acquiring scrolls
Search ordinary floor treasure and monster drops, and check the pawn shop when it refreshes. A blessed scroll of acquirement is the reliable way to request a particular scroll; an uncursed acquirement only chooses the scroll category and then gives a random type. Blippers carry scrolls of teleportation, phantasticons carry scrolls of true sight, and necromancers can leave scrolls of spells.
Using scrolls
Identify both the scroll type and its BUC state before committing rare or dangerous copies. Keep escape effects such as teleportation available for emergencies, use temporary combat or vision effects shortly before they matter, and save acquirement or wishing until the desired result and any required input are known. Choose targets before reading: once a scroll reaches its effect, backing out of a later prompt normally still consumes it. Some scrolls ignore BUC while others reverse their benefit, so consult the individual effect table rather than assuming that blessed is always stronger or cursed is merely weaker.
Trivial
The Windows build does not quite produce the design probabilities above. Its project defines WIN32, which makes Omega use the Microsoft C runtime rand(). Microsoft defines RAND_MAX as 0x7fff, so rand() has 32,768 possible return values from 0 through 32,767. Omega then reduces that value modulo 10,000 before scaling it to the requested range.
As a result, residues 0 through 2,767 each have four possible rand() inputs, while residues 2,768 through 9,999 each have only three. Counting the 32,768 return values as equally likely gives these Windows probabilities for the first roll among scroll types:
| Scroll IDs | Windows initial probability per type |
|---|---|
| 0, 1, 3, 4 | 5.090332% |
| 2, 5 | 5.078125% |
| 6 | 4.635620% |
| 7, 9, 10, 12, 13, 15, 16, 18, 19, 21, 22 | 3.817749% |
| 8, 11, 14, 17, 20, 23 | 3.808594% |
The same bias changes the level check. random_range(3) returns 0 with probability 38.970947% and returns 1 or 2 with probability 30.514526% each. The exceptional random_range(100) == 23 test succeeds with probability 1.220703%. Under the same equal-return-value model, the resulting Windows qualification rates are:
| Scroll level relative to source | Windows qualification rate |
|---|---|
| Lower | 100% |
| Equal | 61.504772% |
| One level higher | 31.362738% |
| At least two levels higher | 1.220703% |
This is why the main generation table records the intended design distribution rather than presenting the Windows runtime bias as the rule. See Microsoft's RAND_MAX documentation.
References
- WinOmega source at the documented revision
- NetHackWiki Scroll article (table organization reference; Omega values and mechanics are sourced from WinOmega)
- Microsoft C runtime
RAND_MAXdocumentation