Property of Sekhmet

Dimitri Meeks points out that since the horse was introduced into Egypt from the Near East, it makes sense that horse-riding deities in Egypt are also from the Near East. The most prominent rider is Astarte, who's actually better known from Egyptian examples than from Near Eastern ones. He highlights three in particular:

• Hibis, where Astarte and Reshep are part of the pantheon of Heracleopolis;
  
• Edfu, where a lion-headed Astarte drives a chariot drawn by four horses - Meeks says she is "clearly identified with the goddess Sekhmet";
  
• Tod, where Astarte is shown in the form of Hathor and called "the one who controls the horse".
  

Meeks outlines the connections between these goddesses, royalty, and royal victory in battle - so, for example, at Denderah Hathor is given the title "mistress of royalty and mistress of horses".

Other gods were also horse-riders or charioteers, such as Horus the Saviour, shown in cippi riding a chariot drawn by griffins; and Thoth, called "master of horses" in a Ramesside inscription. Also at Tod, Raettawy is called "valiant in horseback battle".

ETA: Bit more on Sekhmet and royalty. Janet H. Johnson, reviewing Philippe Germond's Sekhmet et la Protection du Monde, discusses Sekhmet's dual character as destroyer and protector, with her violent rage "channeled into annihilating the enemies of the sun-god"; similarly, "the wrath of the king against his enemies was the transferred destructive wrath of Sekhmet being used to maintain Ma'at." It was the king's job, at the New Year's festivities, to make sure Sekhmet was pacified and her anger therefore safely aimed in the right direction.

When it came to ordinary folks struck by the goddess' ire in the form of sickness, Germond suggests, doctors worked alongside her appeasing w'b-priest. OTOH, in Les Pretres-Ouab De Sekhmet Et Les Conjurateurs De Serket, Frédérique von Känel argues that the w'b-priests were themselves medical doctors; for example, in the Papyrus Ebers, the w'b-priest is described taking the patients pulse.

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Clagett, Marshall. Les Pretres-Ouab De Sekhmet Et Les Conjurateurs De Serket by Frédérique von Känel [review]. Isis 76(4) Dec 1985 pp 628-629.

Johnson, Janet H. Sekhmet et la protection du monde by Philippe Germond [review]. Journal of the American Oriental Society, 104(2) Apr-Jun 1984, pp. 361-362.

Meeks, Dimitri. "L’introduction du cheval en Égypte et son insertion dans les croyances religieuses". in Gardeisen, Armelle (ed). Les Équidés dans le monde Méditerranéen Antique (Actes du colloque organisé par l’École française d’Athènes, le Centre Camille Jullian, et l’UMR 5140 du CNRS, Athènes, 26-28 Novembre 2003). Monographies d’Archéologie Méditerranéenne Occasional Publications 1, 2005, pp 51-59.

Skim-read a slender volume called The Beginnings: Egypt and Assyria (Dawson, Warren R. - Hafner, New York, 1964), the first volume of a series on medical history called Clio Medica. Originally published in 1930, it has little to say about Mesopotamia, and makes no mention of Sekhmet, which surprised me. Nonetheless it was a fascinating read, particularly about the medical ideas of *cough* "primitive" peoples. In some cultures, apparently, human beings are understood to be immortal, unless someone actively kills them; either through violence, which is visible and obvious, or illness, which is invisible and mysterious. Precisely because the source of sickness can't be seen, it must be caused by spirits, whether malevolent demons or the dead (or by witchcraft). Dawson traces the shift in medical thinking from mostly relying on incantations which threaten and repel the spirits, to mostly relying on treatments - including, thanks to trial and error, some medicines which would genuinely work. These early doctors weren't fools. In fact, their "invisible agents" idea is technically correct.