Osiris rules agriculture, fertility, irrigation, law, vegetation, cultivation, viniculture, reincarnation, Earth mysteries, pacifism, eternity, the dead, the underworld, the afterlife, the Inundation, the inner planes, the Nile River, the Mediterranean Sea, the growth of plants, every form of moisture, and life after death.

Osiris is the Greek rendering of his Egyptian name, Asar, which is also spelled Ausar, Usar, Osar, Usire, and Wesir. Other names for Osiris include Khenti, Khenti-Amenti or Khenty-Amentiu, Osiris Khent-Amentet; Unefer, Unnefer, Un-Nefer, or Wennofer; and Osiris Unnefer, Osar-Un-Nefer, or Ausar Unnefer. He is called Sep when dismembered, Khenti-Amenti in death, and Seker when resurrected. He is also Osiris Ankhti, Osiris Saa, Osiris Orion Saa, Osiris Bati-Erpit, Osiris Ptah, Osiris Sekri, Osiris Netchesti, Osiris Atef-Ur, Osiris Taiti, and Un-per Osiris. Gnostic Christians called him Osoronnophris. During the Ptolemaic period, to create a synthesis of Greek and Egyptian religion, Greeks syncretized Osiris with the Apis Bull to create the composite god Serapis, a more macho version of Osiris.

Serapis rules action, Nature, and weapons. Variations of his name, which can be translated as ëunderworldí, include Ser-Apis, Sri-Apa, Ausar-Apis, and Osar-Apis. His planets are the Sun, Pluto, Mercury, and Earth, which is also his element.

Osiris has many titles and epithets, including Lord of Life, Lord of Wholeness, Lord of All, The Begetter, Beautiful Being, Dweller in Peku, Dweller in His City, Dweller in Re-Stau, Osiris in His Habitations in the Land of the North, Dweller in the Hall of the Cow, Osiris Upon His Sand, Osiris in Battle, Osiris in the Water, and Prince Osiris, Dweller in Temples. As a vegetation god, Osiris is called Grain of the Gods. He is called The Great Green as god of the Mediterranean Sea. As god of the Nile and the Inundation he is Osiris of the Mysteries, Who Springs From the Returning Waters.

In his Underworld aspect, Osiris is called The Black One, Bull of the Underworld, Dweller in the Funeral Mountain, and Khenti-Amenti, Foremost of the Westerners. In his aspect as the god of eternal life, Osiris is called Lord of Eternity, Lord of Everlastingness, and Golden One of Millions of Years. As the god of the potential of life after death, his titles include Lord of the Acacia Tree, The One in the Tree, and The Solitary One in the Acacia.

Green and black are the colors of Osiris. He is often depicted with either green skin or black skin. When his dead body is depicted, it often has an erect phallus. Orion is his star. His symbols include the crook and flail of kingship, the atef crown, his own mummified form, a vessel of water, and the white crown of Upper Egypt. The tet, a vertical column with four crosspieces representing the cardinal points, is one of his symbols. It represents stability and his backbone, and figured in the annual Raising the Backbone of Osiris ritual.

The ape, bull, ox, ram, pig, crocodile, griffon vulture, phoenix, and sphinx are all sacred animals of Osiris. Sacred plants of Osiris include ivy, reed, grapevine and grain, particularly wheat and barley. His sacred fruits include dates and coconuts. His sacred trees include cedar, fir, sycamore, tamarisk, pine, every type of palm tree, and the acacia, his death tree. Orion is his star.

All types of grain are sacred to Serapis. The bull is his primary sacred animal; snakes are also associated with him. He was depicted as a bull-headed European man with curly hair and a beard, or symbolized by a large serpent. His worship became especially popular with soldiers in the Roman Empire.

Many different festivals of Osiris were celebrated through the ages, in different parts of Egypt. These include: January 1, January 20 (rejoicing for Osiris), February 11,  February 13, April 14, May 2 (going forth of Osiris), July 14 or July 27 (nativity of Osiris), July 19 (sacred marriage of Isis and Osiris), August 17, September 2, September 5 (raising the backbone of Osiris), September 24 (planting season begins; death of Osiris), September 28, October 3 (lamentation of Isis and Nephthys for Osiris), October 16 (celebrating Osiris Khenti-Amenti), October 27, November 12 (Isis seeks the body of Osiris), November 13 (Isis grieves for Osiris), November 14 (Isis finds the body of Osiris), and December 25 (alternate nativity of Osiris).

Invoke Osiris for civilization, enlightenment, fertility, justice, regeneration, agriculture, judgment, blessings, dignity,  music, dance, earth magic, correct conduct, earth mysteries, legal matters, wise rulership, spells and rituals which relate to the spiral of life, growing grapes, making wine, making farm implements, and teaching by example. He can also be invoked for learning not to be too trusting, and attracting a strong wife. Invoke him as Khenti-Amenti for magic, and as Serapis for fertility, healing, tarot, earth magic, blessing weapons, and for spells and rituals which relate to the afterlife.

Appropriate offerings to Osiris include incense, flowers, meat, wine, ale, pine cones, dancing, and vases of water. The first day of the New Moon is a powerful time for the worship or invocation of Osiris. The night of the Full Moon is a traditional time for celebrating Isis and Osiris. One way to honor Osiris is to make a mummy-shaped poppet of linen cloth, stuff it with grain, and bury it in springtime. Keep it well watered, and unearth it in the summer or autumn. It is a good omen if the grain has sprouted.

Nighttime sacrifices were offered to Serapis in ancient times. Feasts and banquets were often held in his temples. The music of many flutes, and fanfares of trumpets, are also appropriate offerings to Serapis.