Step One: Calling the Elemental
Elementals must be called to be bound; elementals summoned simply return to their native planes when the duration of the summoning is up, even if they have since been transferred to an item. If the summoned elemental is trapped within a magic circle and an attempt is made to transfer it directly to an arcane matrix, it escapes to its home plane in transit. The most common spells used to bind elementals are the planar binding spells.
To bind an elemental to an item requires a spellcaster capable of casting a planar binding spell of the appropriate strength. The particular version of the spell varies depending on the purpose and strength of the intended item.
Step Two: Transferring the Elemental
Once an elemental has been successfully called and bound, the process becomes slightly more complex. Transferring the elemental to an item requires the participation of at least two spellcasters. The item must be physically complete (fully built ship, completed steel defender, etc.) to receive the elemental, and it must have been created with space allowed for the Khyber Dragonshard.
The first step is acquisitioning the appropriate Khyber Dragonshard.
The shard accomplishes two key goals. First, it forms the focal point for a lattice of energy -an arcane matrix- that traps the elemental in the elemental item. The ordered structure of the crystal essentially forms a maze with no exit, which the elemental follows endlessly as long as it remains within the item. Second, this structure acts as a conduit for the elemental's raw energy. As the elemental is forced through the crystalline lattice of the arcane matrix, it gives off energy, which is then transferred to the item.
The size of the dragonshard is not necessarily in proportion to the size of the elemental within it. However, larger elementals are more easily bound into larger shards.
The average Khyber shard used for weapon and armor manufactory is 1-3 inches thick. Typical shards for elemental vessels are, at minimum, 8 inches thick and more than 14 inches long.
Transferring an elemental of a particular size has no effect on the final powers of the item. However, binding a larger elemental does reduce the cost of creating the item.
The second step is gathering the Flow.
The first spellcaster, called the shak'krek (A gnome word meaning 'flow-gatherer') is responsible for releasing the elemental from its binding and holding it, through force of will alone, for just a few seconds.)
Mechanically, this will be a dice roll. 1d20 + Spellcasting modifier against a DC based on the strength of the elemental. A shak'krek can hold an elemental for five minutes per caster level.
If the shak'krek is disrupted from their concentration in any way, they might lose control of the elemental. If this happens, the elemental is immediately freed, and is likely to turn on the shak'krek and anyone else in the vicinity.
The third step is called Tying the Knot. This is where the second spellcaster comes in, called the Hevrae (Gnome for 'one who ties knots'). They will bind the elemental into the object, transferring it from the grasp of the first caster into its receptacle. The shak'krek is necessary in this process because the Hevrae cannot break the wards of the binding and simultaneously transfer the elemental. Doing so requires too much concentration, and to falter even a bit in the transfer would release the elemental.
Transferring an elemental into an item takes 20 minutes, and once the process is begun, it cannot be halted. To complete the transfer, the hevrae must make a roll, 1d20 + their Charisma Modifier, contested by the same check made by the elemental.
The check becomes more difficult when attempting to bind a large elemental to a smaller Khyber Dragonshard.
Note: The process is approached differently for Elemental Vessel Binding