Bind elemental

In order to cast this spell you must have both a creature of the Elemental type that is trapped inside an inverse Magic Circle, and a magic item that is being crafted by you the caster that has not yet been completed. Once the spell is cast the Elemental has to make a Wisdom saving throw to avoid becoming bound to the item. Elemental creatures with an Intelligence ability score of 7 or higher have advantage on their roll to resist being used in this way. If the Elemental fails its saving throw it becomes part of the magic item and contributes to its creation or is imprisoned.

Binding an Elemental to a magic item during its creation reduces the cost to craft the item by 500 Gold Pieces for each CR of the Elemental that is bound to the item. Elementals with a CR of less than 1 will contribute only a fraction of this value. (A CR 1/2 Elemental only adds 250 GP worth of value to the process.) This cost reduction does not reduce the time needed to craft them item, or its overall value, only the amount of gold that is needed to be spent on crafting the item. 

Generally an Elemental is used when crafting an item which is related to that specific type of element, such as a fire Elemental for a Flametongue weapon. However the elemental energy can be used to power most enchantments. When an Elemental type creature is bound to a magic item in this way it is destroyed in the process, and is completely killed once the item's creation is completed. if the magic item is destroyed before it is finished being crafted the Elemental is released and is free. 

This spell can also be used to trap an Elemental type creature inside an object such as a specially prepared and enchanted flask or gem. If this spell is used in this way the Elemental is not destroyed or killed, but is instead trapped inside the item until it is released. Most casters will also try to enchant the object with some sort of spells to provide the person who releases the Elemental some hope of controlling it, however this is not necessary. An item that is being crafted with the sole purpose of being a prison for an Elemental type creature costs a minimum of 500 Gold Pieces to craft for each CR rating of the elemental that is going to be imprisoned. Creating an item like this requires proficiency with Jeweler's tools as well as the Arcana skill, and takes 1 work day to craft for every 50 gold pieces that the crafting materials cost. (500 GP/CR of the elemental + 10 work days /CR to craft) 

While imprisoned inside an item in this way the Elemental will be aware of the passage of time, and for sentient Elementals being imprisoned for long periods of time may cause them to behave erratically when released.