Base tiers

Diablo II's Normal / Exceptional / Elite, one rung longer and named for the four difficulties. The tier is what an item IS underneath; quality is what was rolled on top of it.

Two independent axes

Axis	Values	Decided by
Base tier	Normal, Nightmare, Hell, Torment	The item level it was generated at
Quality	Basic, magic, rare, set, unique, primal	Its own rolls - see Quality and affixes

Every quality can appear on every tier. A Torment basic and a Normal primal are both ordinary finds, and nothing ever stops dropping.

The scales

Multipliers against the Normal-tier numbers shown in Base items.

Tier	ilvl band	Damage / armour	Requirements	Durability	Value

Requirements climb more slowly than power on purpose, so a deep-tier base found early is something to grow into rather than a wall. Value climbs steeply because a deep-tier base is worth real gold at a vendor - and, once salvage exists, real materials.

Which tier a drop gets

Of the tiers an item level allows, the deepest is the most likely. Reading from the top down the weighting is - so at ilvl 1-24 only Normal exists and the table collapses onto it, while at Torment depth all four are in play.

ilvl band	Normal	Nightmare	Hell	Torment

The tail is deliberate. Lower tiers keep dropping at every depth, so a shallow base is always available as a socket host - the cheapest item in the game is the one runewords are built on. They are also salvage feedstock: a plain drop you would once have left on the floor is a White Scale.

How the tier is chosen

The tier is derived by hashing the item's seed, not by drawing from the random stream. Every generated item is reconstructible from its seed - the multiplayer pack and the character-select preview both replay it - so a draw inserted at generation would shift every affix roll after it and silently change what existing seeds produce.

Applied on fresh generation only. A replay rebuilds the pre-tier item, which single-player never keeps: the save holds every stat, and load overwrites the rebuilt copy immediately.

Vendors

Shops stock tiered gear too. Vendor item level is the vendor's own level lifted by the difficulty block:

Difficulty	Vendor ilvl	Highest tier
Normal	6-16	Normal
Nightmare	30-40	Nightmare
Hell	54-64	Hell
Torment	78-88	Torment

A stocked item is tiered on a flat chance rather than by the dungeon's weighting - 35% by default, tunable as Vendor Tiered Stock Chance. A shop is a repeatable source; if every Torment shelf were Torment-tier the dungeon would stop being where gear comes from. An item whose tiered price would exceed the vendor's cap simply stays Normal, which keeps the cap meaningful and keeps the premium vendor's unbounded retry loop from spinning.

Where the tier shows

In the item description, on its own line above the item level, in its tier's colour: white for Normal, blue for Nightmare, yellow for Hell, gold for Torment. The item's name is deliberately untouched - the engine composes magic names against a width budget and falls back to the base's short name when they overflow, so a tier word in the name costs the item its base name.