Orb of Binding upgrades a normal item to a rare item with up to four linked sockets.
Note: If used on an item with more than four sockets, those extra sockets will be lost.
As the example shown above, an Orb of Binding crafts a normal Spike-Point Arrow Quiver into a new rare item.
From PoE 3.14, Orb of Binding has been added to the core drop pool. If you are lucky, you can obtain in common place.
Orbs of Binding drops in Vault rooms in the Temple of Atzoatl.
Binding Shard is a currency item. A full stack will be combined into a Orb of Binding.
Binding Shard drops from areas with Harbingers modifier.
The price of Orb of Binding is about 0.5 Chaos Orb.