Assortment of Mystical

Assortment of Mystical, or ARM for short, are an artifact or mystical object originated from the faraway location, The Land of ARM-Heaven. ARMs are one of 10 main powers available in the Universe of Vinland Kingdom.

Summary
ARMs are artifact known by every residence born in the land of ARM-Heaven and used by almost all and used for a wide variety of purposes. But since the 1st Marchen war, their weaponry efficiency in warfare matters was introduced, and from then it's been popularized. And now, in the land of Vinland, almost all ARM are used as a tool for war and battle, although some of them still used as a "daily life helper", such as additional storage.

ARM were arrived in the land of Vinland 7 years after 8th Marchen war, not the physical ARM, but only on a grimoire containing the way to create such artifact. But only a few wizard in the land of Vinland could understood the Grimoire, specially the one who had lived in the land of ARM-Heaven before coming to the land of Vinland.

ARMs are usually had a great power to begin with, but not all person could use it. Only a wizard with a certain kind of power, and enough magic capabilities could use it. However, if someone has too much magic capabilities, the ARM could break.

Also, ARMs are manufactured through the use of a special metallurgy, giving them a special power in a form of normal accesories. Also, ARM's power could be upgraded by the use of Magical Stones, giving them the boost of power.

Ability
ARMs have a wide variety of ability, depending on the ARM itself. But usually one ARM only has one ability, although some of them could have two abilities or more. A unique ARM has a totally unique ability, as well as it's own unique characteristics. Some ARMs only has a simple ability and used as a mere simple tool. Some ARMs could be used as a weapon, with an appropriate ability as well. Some ARM could transform into a bigger size than it's unused form when activated.

Usage
Although ARMs have a great power, the power output of ARMs are depended on the user's magic capabilities, mental, and physical. A person with magicless blood doesn't have the ability to use a powerful ARMs, or in case he/she uses a weak ARM, the effect is minimal. But if someone has too great magic power, he/she could break the ARM, as shown by Sienna Fisichella, as she breaks an ARM when trying to use it, because she has too much magic power as she holds the power of a spirit. This means that there's a limit on how much an ARM could handle the user's magical power.

When someone could fully synchonize with an ARM, he/she befits the title of ARM user. His/her power will increase when he/she fight, and so on the ARM. However, this could be fatal flaw to someone that uses elemental Nature ARM. As an ARM user synchronized with the ARM, the user's body also adapt with the characteristics of the said ARM, but become weak to the ARM's anti-element (ex : a Flame ARM user becomes weak to water).

It also shown that an ARM won't be compatible with a power user, such as slayer magic and Aura/Nen. The cause is still unknown, although some cases had been happened in the past. For example, Nibutani could not synch with a nature ARM she possess, although she had an Ice Devil Slayer Magic, and an Ice-elemental nature ARM, yet she still couldn't  sync with it.

Classifications
ARMs have a wide variety of power, ability, strength, appearance, and are classified into many kinds. Some of them has a unique ability, some of them are could be used as a weapon, and some of them are could give "curse" to the user.

Guardian ARM :: An ARM that could summon a monster, or a guardian, to protect the owner of the ARM. The drawback effect is, when a Guardian ARM is active, the user couldn't move from the spot he was in when he activate the ARM, and couldn't do anything except deactivating the Guardian ARM.

Weapon ARM :: An ARM that could be used as a weapon in battle. It has an abilty related to weaponry, or an ability to strengthen the attack power, which makes them stronger than normal weapons, by any means.

Holy ARM :: An ARM that possess the holy power, a power to heal and undo curses inflicted by darkness ARM.

Darkness ARM :: An ARM used to curse other people, but with a cost to the user, such as eyes (become blind), voice (can't speak anymore), or even costs life.

Dimension ARM :: an ARM that could teleport someone to other places, and create pocket dimensions as an additional storage.

Ghost ARM :: an ARM that attached to the user's body, and makes the user could use his/her body as a living weapon.

Nature ARM :: an ARM with a power to manipulate certain elements, or enhancing the user's body performance.

Unique ARM :: an ARM that could not be put into ARM category above. They have a unique traits and abilities, which the other kind of ARM don't have. The example is Rena Takamachi's Unique ARM Raising Heart that has the ability and form simillar to her Sacred Gear (with the same name), but it breaks after first use.