Quincy are the primary form of spiritually-powered humans. They are humans whose power comes not from within them, but from around them. All Quincy effectively have a "core" of Reiryoku within them. This is located in the same place as a Saketsu on a Shinigami. The way the Quincy work by taking their innate Reiryoku and forming a Spirit Weapon by focusing on an item in their possession—usually a stylized cross.
Quincy, due to the fact of them not being spiritual being, have mostly fought at range. Most Quincy use their Spirit Weapon in the form of a bow. Contrary to popular belief, Spirit Weapons can be of any shape. Spirit Weapons will absorb Reishi and then turn it around to fire blasts of energy called a "Sagittae." As bows, this usually comes out in the form of arrows. With a weapon such as a lance, it would likely be in the form of an almost column-like blast. All Spirit Weapons are capable of harming spiritual creatures without firing their Sagittae, even bows. Although quickly-formed spirit weapons have an appearance of energy matching the color of their Reiatsu, if given time to manifest they can have a very detailed physical appearance. If the Sagittae are shot continuously, they can eventually injure the wielders' hands.
A Quincy's Reiryoku is used for only two things: as a focus and to power their Judicium—the pinnacle of Quincy power. Similar to Bankai or Resurrección, Judicium is a presonalized form unlocked with dedicated training.
Attaining Judicium is extremely difficult. Most Quincy permenantly lose their abilities while trying to attain it. As there is no "calling back" like Resurrección or second spirit with a Zanpakutou, Judicium has only one way of tapping into that level of power: to overwhelm the soul itself with incredible amounts of Reiryoku. It's possible for a Quincy to quite literally pop like a balloon if they overdo it. Additionally, one's Judicium can activate on its own when the user is surrounded by high concentrations of Reishi and does not possess full control over it.
Judicium takes on a variety of forms, but most commonly gives its user an angel-like appearance, with wing-like Reishi constructs and a star-like Quincy Cross for a halo. It is of note that if this halo is destroyed, the Judicium is cancelled and the user is reverted to a normal state. However, not all Judicium take these appearances, but there is always something to represent the halo. A Judicium's abilities come from something the user believes strongly combined with their own personality. This means that a Judicium can take another form as beliefs change in the future.
Skills:
Reishi Control: Simply put, this determines how well a Quincy can manipulate Reishi.
Sagittae: Saggitae is the energy attacks given off by a Quincy's Spirit Weapon. The higher the skill in this, the more that can be fired off and the stronger each one can be.
Alchemy: The primary form of Quincy spellcraft. By combing Reishi and Reiryoku with various other materials within specially-made tubes (commonly called Gintō [銀筒, Silver Tubes]), they are capable of creating different effects. A lot of this comes down to spiritual chemistry. Doing so outside of the Gintō can be extremely volatile due to Reishi's poor reaction to atoms.
Varico: Also known as Hirenkyaku, Varico is the Quincy movement technique, allowing the user to move at high speed by riding on the flow of Reishi created below their feet. Essentially, it is the Quincy equivalent to the Shinigami's Shunpo and the Arrancar's Sonído. To perform this technique, the user gathers Reishi under their feet and rides them to the desired location. Like the air-walking skill displayed by most Arrancar and Shinigami, it can be used to hover or fly over long distances.
Equipment:
Quincy Bangle (装身具, Sōshingu; lit. "Body-Dressing Element"): The Quincy Bangle is an artifact designed to mimic a Quincy's natural powers. It works by drawing in Reishi from the environment, much like a Quincy does regularly. It is mainly used to help new Quincy who have not gotten a good hold of manipulating Reishi.
Hollow Bait: This item is a small, coin-shaped disk that attracts Hollows when crushed.
Seele Schneider: The Seele Schneider is a thin, silver-colored weapon which, when activated, sports a glowing blade the same color as the user's Reiatsu. It functions much like a chainsaw, with Reishi making 3 million round trips per second around the edge of the blade. The vibrations of the Seele Schneider are not just for cutting. Through its vibrations, the Seele Schneider loosens the bonds between the Reishi of whatever it cuts in order to make them easier to capture. The Quincy fight by gathering the surrounding Reishi and using them as their own personal weapon, and the most powerful manifestation of that is the Seele Schneider. The Seele Schneider is not a sword, but an arrow.