Drop Explorer

• Monster level by areaderivedlevels.txt MonLvlEx(N) / MonLvlEx(H); monstats.txt Level, boss, NoRatio; the met-in rule of pipeline/gamedata/world.mjs (lib/tools/monster-level.ts)build 3.3.93847 · verified 2026-10-08 · high confidence

  A monster's level is its monstats.txt Level for the difficulty — except that on Nightmare and Hell a monster without the boss or NoRatio flag takes the level of the area it is met in (levels.txt MonLvlEx), so the same Bone Warrior is level 77 in the Tower Cellar and 85 in the Pit. Act and quest bosses keep their table level (Baal 99 on Hell); a super-unique is its type at its home area + 3; champions are +2, random uniques and their minions +3; a Terror Zone lifts the level first. Every tool resolves the level through the one rule, defaulting to the monster's first area in the game's order and offering the others where the level differs. A superunique's home area comes from a hand table (data/boss_behaviors.json, legacy), not from the map files.

  The game's rule (D2Game monster init; D2MOO Monster.cpp). The areas a monster is met in are its nmon spawn lists, the preset areas and super-unique homes, and its leader's areas for a minion — asserted equal to /data/monsters when data/tools/xp.json is built (integrity audit 2026-10-08, root cause 2).

• Quality checksderiveditemratio.txtbuild 3.3.93847

  c = (ratio − (item level − base level) / divisor) × 128; then × 100 / (100 + effective Magic Find); at least the row's minimum; then less c × the TC's quality factor / 1024. The check succeeds with 128 / c, in the order unique, set, rare, magic. A Shako from Hell Mephisto at 0 % Magic Find is about 1 in 14.9 per check.

• Magic Find returnslegacy ruleD2MOO (the game's code, decompiled)

  Magic Find counts in full for magic items, and for every quality up to 10 %; above 10 % it has diminishing returns for the others: MF × 250 / (MF + 250) for unique, × 500 / (MF + 500) for set, × 600 / (MF + 600) for rare.

• Which ratio rowgame tableitemratio.txtbuild 3.3.93847

  The expansion rows apply. The Uber row is for exceptional and elite bases, the class-specific row for class items; the monster's rank does not choose the row.

• No drop with playerslegacy rulePhrozen Keep treasure-class guide

  With n players N = (n + 1) / 2, rounded down; the no-drop weight becomes total / ((no-drop + total) / no-drop)^N − 1, floored.

• Treasure-class upgradederivedtreasureclassex.txt group / level; D2MOObuild 3.3.93847

  On Nightmare and Hell a monster's treasure class moves down the rows that follow it in the table while they are in its group and their level is at most the monster's level. Bosses never upgrade (monstats boss, NoRatio), nor does anything on Normal; a Terror Zone's Desecrated classes always do.

• Item groupsderiveditemtypes.txt TreasureClass and Rarity, item levels; D2MOObuild 3.3.93847

  weap, armo, mele, bow and abow groups (3 to 96) hold every spawnable item of that kind whose level, rounded up to a multiple of 3, is the group's number — no quest items, no throwing potions — weighted by its item type's Rarity (at least 1), not the item's own.

• Negative pickslegacy ruleD2MOO (the game's code, decompiled)

  A negative pick count runs the entries in order, each as many times as its weight, with no no-drop roll — and stops when the weights run out, even with picks left.

• Six itemslegacy ruleArreat Summit

  One kill drops at most six items; later picks are lost.

• Quality factors down the walklegacy rulePhrozen Keep treasure-class guide

  A treasure class's Unique, Set, Rare and Magic factors pass down to the classes it calls; where two meet, the higher one holds. The lab carries them to every item, so a Mephisto drop reached through his 983 factors keeps them.

• Item level of a killlegacy ruleArreat Summit; desecratedzones.json

  An item's level is the level of the monster that drops it — on Nightmare and Hell an ordinary monster's is its area's (Monster level by area): champions 2 above their type, uniques, their minions and super-uniques 3 (a super-unique at its home area's level + 3 on Nightmare and Hell). In a Terror Zone the monster is first raised to your level + 2 within the zone's bounds; a herald adds its tier's treasure-class boost. The treasure class upgrades at that level.

• Runs an hour and the chance over timederivedthe per-kill chance above; your run timebuild 3.3.93847

  Runs an hour = 3600 ÷ seconds a run. A run's chance = 1 − (1 − per kill)^kills of the target in the run. The expected runs to the first drop is 1 ÷ that chance — a mean, not a promise: half of all farmers need more than the median run count, and 90 % and 99 % take the runs shown. The chance in an hour or in ten is 1 − (1 − per run)^runs.

• At least one in n triesderivedprobability: independent triesbuild 3.3.93847

  Each run is independent and the odds never improve after a miss: the chance of at least one drop in n runs is 1 − (1 − p)^n, and n for a given confidence c is ⌈ln(1 − c) ÷ ln(1 − p)⌉.

• Odds per killderivedtreasureclassex.txt, itemratio.txt, uniqueitems.txt / setitems.txtbuild 3.3.93847

  Per pick, each item's chance is the product of the shares down its path; a unique or set item multiplies its base by the quality check (with the factors in effect) and its share among the uniques or set items that fit the item level. Per kill, the picks run in the game's order — a sequence's entries one after the other, a nested class's picks in a row — and an item counts when it shows among the first six drops.

• Which uniquederiveduniqueitems.txt / setitems.txtbuild 3.3.93847

  A unique roll picks among the base's spawnable uniques whose level is at most the item level, weighted by rarity; with none it becomes a rare (a set roll becomes magic).

Sources: treasureclassex.txt, itemratio.txt, itemtypes.txt, weapons / armor / misc.txt, uniqueitems.txt, setitems.txt, monstats.txt, superuniques.txt, levels.txt and desecratedzones.json of build 3.3.93847 (data/tools, pipeline/build-tools-lab.mjs).

• Per-kill odds treat a nested treasure class with several picks as independent draws, so the six-item cap is exact only when every pick drops at most one item.
• On Nightmare and Hell an ordinary monster takes the level of the area it is met in (pick the area where it has several); a pack that wanders into the next area keeps the level of where it spawned, which the lab cannot know.
• Super-uniques sit at their home area's level + 3; a few have no home area in our tables and use their type's level + 3 (marked).
• A minion rolls its type's regular treasure class at its leader's level + 3, and a herald the Terror Zone level + 3 with its tier's treasure-class boost — published rules, not table facts.
• Life on the dossier is the monster type's at that level, before the champion, unique and players bonuses.