Celestial Spirit Magic

Celestial Spirit Magic is a Holder Magic and a type of Spatial Magic used by Celestial Spirit Mages that involves the summoning of Celestial Spirits.

Description
Celestial Spirit Magic is a type of Magic in which the user summons Celestial Spirits by opening their gates through the use of Celestial Spirit Gate Keys. These Keys are separated into two classes: the more common Silver Keys and the rarer Gold Keys. Keys for Celestial Spirits are counted in Units (collectively without regard of Gold or Silver), and a Celestial Spirit Mage is noted by how many Units they have obtained.

Contracts and Rules
When a Celestial Spirit Mage receives a Key and opens its Celestial Gate for the first time, they have to set up a contract with the respective Spirit. This contract consists of asking the Spirit which days it can be summoned by its contractor. This simple agreement leads to a dedicated and serious bond between the Spirit and summoner. However, under certain circumstances, i.e. during battle, and a Spirit is summoned for the first time, the making of a contract may be suspended on a later date. Contracts can be broken if the Mage gets arrested, releases the Spirit by themselves, or dies. When a Celestial Spirit Mage summons a Spirit, it appears directly next to them, as that's where the gates to the Spirit world had been opened. It's impossible to summon spirits elsewhere.

The Spirits must also abide by certain rules enforced by the Celestial Spirit King. The only rule that has been introduced in Fairy Tail so far is that a Spirit may not directly or indirectly kill its summoner under any circumstances. When the Gates are closed, it is required from both the summoner and the Spirit to agree upon the gate's closure. However, Spirits can also be "forced closed" in battle, which means they can be forced back into the Celestial World by the summoner's will, though not every Celestial Spirit Mage is capable of doing such.

Celestial Spirits also have different categories of sorts that fall under the basic summoning conditions from their owner. For example, Loke summons himself most of the time without Lucy Heartfilia doing so herself; Virgo has also summoned herself various times, as have Gemini, Aquarius, Taurus, Plue, Horologium, Capricorn and the Eclipse Celestial Spirits. Also, if the trust between the Celestial Spirit and the owner is not an issue, contracts can be temporarily dissolved. It also seems that if the Celestial Spirit is strong enough, they can employ their own Magic to stay in the Human World, when/if the contract is not in action. Additionally, a Celestial Spirit may grow stronger if their summoner grows stronger in terms of Magic Power.

Spells and Abilities

 * Force Gate Closure: Closing the gates requires a mutual agreement from both the summoner and the spirit. However, some Celestial Spirit Mages have demonstrated the ability to force the gates to close in battle, compelling the Spirits to return back to the Celestial Spirit World.
 * Multiple Summons: Summoning more than one Celestial Spirit uses up a lot of the summoner's Magic ability which may even lead to their death. However, some Celestial Spirit Mages have shown the unique capability to summon multiple spirits at the same time. If one is capable of this feat, it provides greater flexibility as he/she is able to combine the strength and abilities of their spirits for more powerful attacks. They can also use their own Magic in combination with another spirit to increase the power of an attack.
 * Celestial Fireworks: By twirling any Gate Key, the user can make fireworks of a golden color.
 * Recompense Summoning: A technique that makes possible for a Celestial Spirit Mage to summon the Celestial Spirit King, who does not have a physical key, but there are certain conditions to do so. The first condition is that the Celestial Spirit Mage must have enough Magic Power to summon at least three Spirits of the Zodiac at once. The second is that a Golden Zodiac Key must be sacrificed to do so. The final condition is that the Mage and the Spirit of the Key must have a high level of trust between them. Whichever Key is sacrificed to summon the King will then crumble to pieces, and will henceforth be unusable. As such, the Spirit of the Key will no longer be able to travel the Mage's world. Therefore doing so is considered the very last resort.
 * Telepathy: On a couple of occasions, spirits have been shown to be able to communicate with their owner (via their keys) without being summoned.
 * Self Summoning: On various occasions, some spirits have been shown to be able to summon themselves without the need of their owners. Notable spirits include Loke, Horologium and Virgo.