Devices (デバイス Debaisu), a kind of Magical Terminal (魔導端末 Madō Tanmatsu), are ubiquitous and extremely versatile tools used by the mages of the Nanoha universe. Although, given the series' focus on magical combat, most depicted Devices are used and treated as weapons, it is not the case for the vast majority of mages working in more peaceful professions. The basic function of any Device is to augment their master's magic abilities and assist them in casting spells. Since magic in the Nanoha universe is very similar to information technology, these sophisticated magical "computers" take over tasks that the human brain cannot handle efficiently enough, such as recording and reproducing the spells that the mage has cast.
The exact methods of Device creation are unclear. Apparently, it doesn't require complex machinery but specialized skills are needed to construct and maintenance Devices efficiently. Low-end Storage Devices for regular mages are probably mass-produced by the TSAB, but all high-end ones are hand-crafted. Many mages therefore rely on specialists ("Device Meisters") like Mariel Atenza and Shario Finieno to create and upgrade their Devices.
All Devices in the series have distinct appearances and color schemes, moreso for high-end units. Upon the Device's first activation, its master additionally gives it a unique name.
Because of the very close interoperation between the mage's brain and their Device, both have to be attuned to each other upon the Device's first activation, and regularly recalibrated to ensure optimal performance. For this reason, most mages keep using and upgrading their initial Devices rather than adopt new, more powerful ones, e.g. Chrono Harlaown continued to use his S2U even after acquiring the much more powerful Durandal. However, Teana Lanster completely abandoned her Anchor Gun in favor of Cross Mirage.
In addition to computational capacities, the Device also assists and regulates the mage's mana output. Two output modes are available: "User Cross Link" (ユーザークロスリンク Yūzā Kurosu Rinku), wherein magical energy is constantly channeled through and stabilized by the Device, and "Direct Boost" (ダイレクトブースト Dairekuto Būsuto), where the mage's magic output is directly strengthened and accelerated.
Normally, a mage uses exactly one Device throughout their lifetime. Some mages, like Yūno Scrya and Lindy Harlaown, don't use a Device at all, since technically, it is not required to cast magic. Yet others, like Subaru and Ginga Nakajima, use two Devices at once, although both have to be synchronized with each other, as well as with their respective master's brain. While most Devices take form of a single object (staff, sword, pendant, etc.), some, like Revolver Knuckle and Cross Mirage, consist of two parts (gauntlets and guns, respectively) that can be used independently of and even against each other.
Should a Device's master die, it is considered masterless until it becomes synchronized with another mage, e.g. Revolver Knuckle was passed down to its late master's daughters. As Agito's example shows, even Devices sophisticated enough to operate autonomously are uncomfortable with being masterless and strive to escape that state. On the other hand, Unison Devices in particular are obviously advanced enough to augment Unison-suited mages they are not technically attuned to (Rein and Signum, Rein and Vita, Agito and Zest Grangaitz).
Because their function is to augment a human brain, all Devices possess a more or less sophisticated artificial intelligence. Depending on the level of AI advancement, the Device is placed into one of the following categories:
- Storage Devices possess the least intelligence but compensate with faster processing speed. They are actually much more commonly used among mages (particularly, regular TSAB enforcement troops) than Intelligent Devices, despite infrequent appearances in the series.
- Boost Devices, introduced in StrikerS, are essentially Storage Devices specialized in a specific kind of Increase Magic called "Boost Up", which gives other Devices power boosts in particular areas. They also seem to be associated with summoning magic.
- Armed Devices are combat-oriented, most weapon-like Devices that are closely associated with Belkan magic and the cartridge system. They are placed somewhere between Storage and Intelligent Devices in terms of AI sophistication.
- Intelligent Devices incorporate sophisticated AIs, enabling them to have a large degree of autonomy, e.g. acting on their own when their master is incapacitated (like Mach Caliber in StrikerS) or requesting specific upgrades (like Raising Heart and Bardiche in A's).
- Hybrid-Intelligent Devices have been introduced in ViVid as a distinct category, though detailed information on them is yet to be released. They appear to be a middle ground between Midchildan Intelligent and Ancient Belkan Unison Devices. They are presumably the same as the "Autonomous-Action Type Intelligent Devices" in ViVid Strike!
- Unison Devices, also known as Unity-Type Devices, have only been developed by Ancient Belkans. They resemble humans, and have AI so advanced that they are treated as fully self-aware and sentient individuals. These Devices can "unite" with suited individuals to provide mana control and assistance according to circumstances.
The classification above does not cover various Device-like equipment. Intelligent, Storage and Boost Devices are used in the Midchildan magic system, while Armed and Unison ones are used in the Ancient Belkan system. The Modern Belkan system mainly uses Intelligent and Armed Devices. Furthermore, a Device may be optimized for a particular kind of magic, e.g. Durandal is specialized in freezing spells.
- Weapon-type are wielded like proper weapons in combat (e.g. Bardiche).
- Wearable-type are worn on the body like pieces of clothing or armor (e.g. Mach Caliber).
- Auxiliary control-type merely enhance their master's magic without being used in combat directly (e.g. Sacred Heart).
Other classifications have been mentioned in the recent installments but not elaborated upon. In Force, Fate's Bardiche is said to have been upgraded to a "5th Generation Device" (第五世代デバイス Daigo Sedai Debaisu), giving it the ability to convert mana into physical energy to counter anti-magical effects, but other Device generations are yet to be described. Likewise, in ViVid, the DSAA Intermiddle requirements include a "Class 3" Device, but other classes have never been mentioned yet.
Most Devices have several forms they can change to at their master's command. The two most common forms are the inactive and active state. In the inactive state (待機フォルム taiki forumu, lit. "standby form"), used for energy conservation, Devices appear as small objects, ranging from gems to cards. Additionally, Devices initiate an auto-repair mode (if required) when inactive, and will automatically deactivate if the damage is significant. In the active state, necessary to cast most magic, they can take a variety of forms, depending on their type and specialization, but the most common one, especially for Storage Devices, seems to be a simple staff. Some Devices can assume different active forms depending on the needs of their masters, though this seems to be reserved only for more advanced Armed and Intelligent models. Armed Devices usually have weapon-like forms, either variations of the same weapon (Graf Eisen's various hammer forms) or several (Laevatein's sword, chain-whip, and longbow forms).
Like the Devices, their master's Barrier Jacket may have several forms, and changes in one can be accompanied by changes in the other (e.g. in Fate Testarossa's case), though not necessarily (cf. Signum, Vita, etc.). Some Devices, like Vivio Takamachi's Sacred Heart, only have one default form, and their activation merely triggers changes in their master's Barrier Jacket. It is unknown whether there is a limit on the number of forms a single Device can assume. Fate Testarossa's Bardiche and Nanoha Takamachi's Raising Heart currently share the record with six distinct forms (including the inactive one) each.
The most powerful form of the Device is referred as its "Full Drive" and often requires considerable mana expenditure to sustain.
Devices generally have the ability to speak, although their coherence and verbosity depends on the sophistication of their AI. For example, an Armed or Storage Device will generally speak in short, choppy phrases, whereas Intelligent or Unison Devices communicate in full sentences. Devices can also be capable of receiving telepathic messages, but this is not a default option, as Steed's example shows.
The language spoken by a Device generally depends on its magic system: Mid-Childan and Modern Belkan Devices speak English; Ancient Belkan Armed Devices, German (which is believed to be the same as the Ancient Belkan language); and Unison Devices, Japanese. However, Strada, a Modern Belkan Device, speaks German, likely due to Erio's specialization as a knight rather than a mage. In any case, the mage is always able to understand their Device, perhaps thanks to their synchronization. Devices tend to address their respective masters and creators with male titles (Master, Sir, Meister) even if the mage in question is female. Ironically, S2U's gender-neutral "Boss" refers to the already male Chrono Harlaown.
Civilian Devices are implied to possess more advanced communication abilities than military ones, as evidenced by Steed's fluent Japanese.
Devices can be further upgraded with optional modules that enhance their performance or add new functions.
- Auto Guard module automatically casts defensive magic spells if the mage is under attack but cannot respond due to surprise or injury.
- Cartridge system allows the mage to temporarily boost their Device's power output by expending "cartridges", capsules of compressed magical energy prepared in advance.
- Accelerate Charge System increases the Device's capacity for high-speed charged attacks.
- Blaster System is an experimental upgrade that provides a continuous power boost to the mage at the cost of severe internal damage to their body and Device.