Diablo II/Horadric Cube

See also: 

The Horadric Cube is an item needed to complete the ../Horadric Staff/ in Act II and ../Khalim's Will/ in Act III. It is first found in a chest guarded by in the Halls of the Dead Level 3 beneath the Dry Hills in Act II; alternatively, it will drop from the second Super Unique Council Member killed in  in Act III for any character that does not already have one in inventory or stash. However, each character can only pick up one.

It requires 2x2 inventory space to pick up. Once in inventory or stash, right-click to open its window on the left half of the screen: it has 4x3 inventory space of its own. Items can also be placed in it by left-clicking on them, dragging them over it and releasing them: they will be moved inside as long as there is enough space. Deckard Cain can identify items stored inside.

It can be emptied quickly by dropping it: its contents will be moved to inventory, provided there is enough space (otherwise, remaining content is dropped as well).

Aside from extra storage, it can be used to create new items or portals, or socket or upgrade existing items: simply place the required input items inside, then left-click on the Transmute button for the desired output. Any incorrect or extra input items will prevent them being transmuted.

Amulets
The Prismatic Amulet also has 1/2 chance of a suffix.

Socketed weapons
Any items in input sockets are destroyed.

Magic throwing weapons can be used as input, but the output will not be socketed.

Polearm
Output is a random polearm of QLvl 50 or less, which means it can be any Normal or Exceptional polearm except a Bec-de-Corbin (QLvl 51) or Grim Scythe (QLvl 55). It also has 1/2 chance of a suffix.

Sword
Output sword is the same type as input. It also has 1/2 chance of a prefix.

Shield
Output shield is the same type as input (which can also be an auric shield or a shrunken head in Diablo II: Lord of Destruction). It also has 1/2 chance of a prefix.

Rings
Output also has 1/2 chance of a suffix.

Rare items
When 6 Perfect Skulls are required, items which require 4x2 inventory space cannot be used as input.

Portal
This portal can only be opened in the Rogue Encampment of ../Act I/ after completing the current difficulty.

Socket rare item
If an item cannot have sockets, this will not add them: only rare helms, body armor, weapons (excluding throwing weapons) and shields can be socketed.