Master-Servant Contract

Master-Servant Contract Magic or just the Master-Servant Contract is a unique magic that was created by Archdemons and Ancient Devils to prepare for their battle against the Vampyres, Seraphs, Heroes and Fallen Angels and it is used by a number of high-ranking devils and other races.

Description
The Master-Servant Contract is a kind of magic that ties the souls of two people together, which also makes them aware of one another's locations. However, it's been shown this can be negated utilizing a barrier as shown when Mina Karnstein was kidnapped by Zephon and taken to his manor.

Activation
Whenever used in the Human World, users of the Master-Servant Contract would need to wait for the full moon in order to either activate and/or cancel it. It doesn't apply in Hell as several High-Ranking Devils, Vampyres, Fallen Angels and even Grim Reapers are able to use it at any time. The ceremony required to activate it entails both Master (主 Shu) and Servant (従 Jū) to stand in the middle of a magic circle, then a magic circle would soon appear on the back of the Master's hand, then the Servant would need to kiss it in order to perform the "Kiss of Devotion", in which the magic circle appears and that would establish the contract.

Effect
Aside from being able to tell one another's location, a curse would activate whenever the Servant either betray or feel guilt towards their master, and is shown by the varied colored collar that appears around their neck. Though the curse, which occurs varies based on whatever magical nature was used in order to form it. Another effect of the contract is that it increases the power of both the servant and the master as the servant's loyalty grows.

Hinami Karnstein, who used her nature as a succubus causes an aphrodisiac that will increase the more the Servant continues to increase the resist their Master, causes them to faint and their brains will even be fried.

Arthur Pendragon, who used his nature to form a Master-Servant pact with Kokichi Kobayashi would result in him being sent to the zero dimension if the curse activates.

Level
There are certain levels in the Master-Servant Contact, which is signified by the specific color of the collar, which appears around their neck: Blue is the lowest and basic, which represent the low trust that a servant has toward their Master. Violet-Blue is the second stage and color that the collar turns, representing their growth in trust in their Master. The second highest is Violet-Red. And the highest maximum limit of the Master-Servant Contract is Crimson Red, which a Master and Servant could reach the Master-Servant Vow.

Variants
Overtime after the Great Mythology War, several variants of the contract began to rise, such as the Evil Pieces system of the Demons. After the peace treaty between the Five Factions, the Brave Saints system, used by the Seraphs, was created by copying the Demon's Evil Pieces system and the Fallen Angel's Artificial Ancient Gear technology.

Evil Pieces
The Evil Pieces, also known as the Devil's Black Pieces, is the Devil's version of the Master-Servant Contract. They are a set of 15 chess pieces given to Demons to increase their ranks by reincarnating other beings into Demons.

Brave Saints
The Brave Saints, also known as the Royal Contract Users, is the Seraph's version of the Master-Servant Contract. They are a set of 13 cards used to increase their ranks by forming a contract with other beings and turning them into Angels. The Brave Saints are based on the Evil Pieces, albeit being based on a suit of playing cards rather than chess.

Trivia

 * The system of the Contract and it's variants is based off a combination of the Evil Pieces and Brave Saints from High School DxD and the Master-Servant Contract from Shinmai Maou no Testament.