Core mechanics

The rules that govern progression and loot. Everything on this page is enforced in code; the numbers are read from the modules that define them.

The three levels

Diablo II keeps three separate numbers where vanilla Diablo has one. This build does the same.

Name	What it is	Where it comes from	Where you see it
alvl - area level	A property of the place. Fixed per floor per difficulty.	`floor + 24 x difficulty`, so 1-96 across the 24 areas	The automap, under the difficulty line
mlvl - monster level	What a monster is worth as a source of loot.	The area level, +3 for a unique, +2 for a champion	Bottom-right of the monster health bar
ilvl - item level	Stamped on an item when it is generated.	The mlvl of whatever dropped it, or the alvl of the chest, floor or shop	The item's description

Why mlvl is not the monster's combat level. Monster::level() drives to-hit, block chance, experience and some missile damage from thirteen call sites. Moving those onto the area ladder would be a combat rebalance disguised as a loot change, so drops ask a separate function and the combat curve is untouched.

What an ilvl gates

Which base items can appear. Every base carries a quality level; a base can only drop when qlvl <= ilvl. See Base items.
Which base tier it is forged at. One tier per 24-level block. See Base tiers.
How good the roll may be. Rare, buffed-unique and primal chances all climb with the band. See Quality and affixes.
Which spell books can exist. A book needs the ilvl its spell's band demands. See Spells.

Spell and skill tiers

Every spell and every class-tree skill sits in one of six tiers, by the character level it demands: . Below its tier a spell cannot be learned and its book cannot be read.

The Rule of Rangs

Each rank of a skill or spell costs one more character level than the rank before it, counting from its own tier:

required character level = tier + (rank - 1)

A tier-1 spell reaches rank 10 at character level 10; a tier-30 skill reaches rank 10 at 39. This is what replaced Diablo II's flat cap of 20 points per skill.

No ceiling. The cap on any single skill is - the entire pool a character can earn, one point per level from 2 to . Nothing is out of reach permanently; depth is paid for in levels rather than forbidden.

Difficulties

Difficulty	Area levels	Base tier	Monster level offset	Notes
Normal	1-24	Normal	+0	The whole 24-floor descent
Nightmare	25-48	Nightmare	+15 combat
Hell	49-72	Hell	+30 combat	Every base item is obtainable by Hell/Hell (alvl 61-64)
Torment	73-96	Torment	+30 x multiplier	Single-player only; the multiplier is an INI setting

Magic Find and Gold Find

Two stats that change what a kill is worth rather than how fast it dies. They come from charms, from gems, and from affixes, and they are read at the moment an item actually drops.

Stat	Does	Where it comes from
Magic Find	A percentage chance that a plain weapon or armour drop arrives as a rare instead, rolled at half-to-full of the drop's own level band	Topaz gems in armour, the Luck charm, magic-find affixes
Gold Find	Increases every gold pile by that percentage, up to the stack cap	The Greed charm, gold-find affixes

Magic Find only upgrades a drop that rolled nothing: basic quality, and no Oracool quality tier. It never touches something that already rolled magic or better, and it cannot make a unique. The base tier is irrelevant - a Torment-tier white sword is upgradeable exactly like a Normal one, because base tier and quality are independent axes.

Progression that outlives your gear

A Signet of Learning grants one permanent stat point, and a character may ever consume of them. The cap is the whole design: without it a signet is a slower level-up; with it the pool is finite, and you can exhaust it and then must live with what you spent it on. The point lands in the ordinary unspent pool, so you decide where it goes.

Signets come from two places. They drop from champions and better only — times what the monster is worth, so 2x that on a champion, 4x on a unique and 6x on a Dread boss, and never at all from an ordinary kill. And they are paid by milestones: things you do once, each worth exactly one signet, the first time and never again.

Milestone

Milestones are the reliable half and the drop is the bonus, which is why the drop is narrow: a trickle from ordinary monsters would be something nobody could aim at.

A signet at the cap is never consumed. It is refused before it is spent, because a capped, permanent, unrecoverable resource silently eaten by a full pool is the worst thing the item could do.

Named encounters

A specific hard fight, in a specific place, with a known reward. A Sealed Map drops from a Dread boss; using it in town opens its encounter and consumes the map, so how often you can run one is bounded by drops rather than by a timer. The floor holds one Dread boss and its escort and nothing else — the encounter is the fight.

Encounter	Where	Counts as floor	Opened by	Guaranteed reward

The reward is guaranteed, not rolled — the map says what its guardian carries, and a roll would make that a lie. Each is a charm, so it competes for the three-charm active cap: carrying one costs a slot rather than filling one, which is what makes three signature rewards a decision.

The map is spent when the encounter opens, not when it is cleared. Leaving before the guardian dies costs you the map.

Ethereal items

A ghost of an item: 35% more damage or armour, half the maximum durability, and no smith will touch it. Any durable weapon or armour can roll ethereal on the drop, at any quality.

The bargain is stamped into the item's own numbers when it drops, so what you read on the item is what you get. There is no repair path - an ethereal item is a thing you use up.

Sockets, in one line

A quarter of plain equipment drops socketed, with as many sockets as it has 28x28 inventory cells - one for a ring, six for body armour or a two-hander. Every base tier can host them, and gems, runes and 370 runewords all live in them. That is a system of its own - see Sockets and gems.

Resistance

Fire, lightning and magic resistance each reduce incoming damage of that school by their percentage. Two rules shape how much of it you can actually hold.

The soft cap sits at %. Up to there a point of resistance is a point. Past it every points of gear buy one point of resistance, up to a hard ceiling of % that nothing exceeds.
Each difficulty penetrates. A fixed penalty is subtracted from your total before any cap applies, so harder difficulties demand more gear to stand in the same place: .
Resistance never goes below zero. Being unprepared costs you the reduction; it does not amplify the damage.

The two rules compose: reaching the ceiling costs raw points on Normal and on Torment.

Character rules

Naked heroes. New characters start with no equipment, no potions and no gold, both buttons on the bare fist. INI-toggleable, on by default, read once at creation.
No vanilla class skills. Item Repair, Trap Disarm, Staff Recharge, Search, Identify and Rage are retired. The class trees carry every skill a class is meant to have.
One skill point per level, spendable on either the spell list or the class trees - both draw from the same pool, and both can refund a rank at a time for free.
Run anywhere. Press R to switch between walking and running, in town and in the dungeon alike. Session state, default off, and the event log says which mode you just chose. There is no stamina bar.
Points can be taken back. A rank at a time, free, from the Abilities window - or the whole pool at once from Adria, for gold.
Auras occupy the right button. Lighting an aura clears the readied right-button skill, and readying a skill puts the aura out. They are one slot.