Exactly what does Kanai's Cube do? Blizzard has posted a new Patch 2.3.0 Preview focusing on the 'Horadric Cube successor' that can "extract a Legendary power" and add it to a collection list.
This is a huge boon to Nephalem who've been hoarding certain Legendary items in Diablo III because of their Legendary perk. Now we can amass them and select to 'equip' three.
We'll have the option to pick one Legendary power from Weapons, Armor and Jewelry categories. These can be swapped out at any time by going back to Kanai's Cube. The choice now is whether you breakdown a Legendary to extract a maximised version of its power.
"This is a huge new feature that will fundamentally change the way you look at an item when it drops. Think of it as the handyman’s (handynephalem’s?) tool for item customization. Not only does it add another layer of character power at your fingertips, but also introduces a structured collection element to the huge item game at the core of Diablo III."
"One of the first, most frequent powers you’ll utilize is the ability to extract a Legendary power from an item. This will add the power to your collection list, a comprehensive history detailing the vast amount of powers you’ve amassed. This also allows your hero to equip a Legendary power without having the item equipped, clearing up your stash of all those items you’ve been keeping “just in case.”"
The other incredible game-changer to Kanai's Cube is the ability to "reforge a Legendary" which rerolls all its stats as if it just dropped fresh. This could result in an Ancient rating, but it could also strip it away.
Those eager to see this power for themselves can hop onto the Diablo III PTR servers and play Patch 2.3.0 before it finally goes live.
Check out the Patch 2.3.0 Preview: Kanai's Cube blog for more.