|Four depictions of the goddess Sekhmet, a lion-headed female, surmounted by a sundisc, holding a snake, ankh, or papyrus scepter (the symbol of Lower Egypt).|
In c.2500BC, in the Pyramid Texts of Unas (line 390), the pharaoh Unas is said to have been conceived by Sekhmet, Sheskhentet, and Sothis. 
In the middle kingdom (2061-1650BC) and new kingdom (1549-1070, Sekhmet was associated with the pharaoh as follows:
“In the New Kingdom, various Egyptian kings were associated with Sekhmet and her violent anger. Thutmose III is called ‘son of Sekhmet’. Amenhotep II is ‘a raging lion’, who ‘triumphed ... like the triumph of Sekhmet.’ Seti I is ‘beloved of Sekhmet’. In the account of the Battle of Qadesh, Ramesses II is in battle, and ‘Sekhmet, the great one, is with him ... on his horse. Her hand is with him.’ Ramesses II is also called ‘Sekhmet in her moment of rage,’ and Ramesses II is ‘Sekhmet when she is enraged’. The competing forces of ferocious rage and a calmer guardianship, which are represented by Sekhmet and Bastet, must be balanced in the person of the king. A Middle Kingdom text that praises the (unnamed) king provides a description of this complex nature. In the text, which we refer to as The Loyalist Instructions, the king is both ‘Bastet, who protects the Two Lands’ and ‘Sekhmet against those who disobey his orders.’ The king embodies the goddess's violent traits and her nonviolent traits, such as guaranteeing crops and alleviating maladies.”— Vanessa Davies (2018), Peace in Egypt (pg. 48)
Sekhmet, in the Egyptian pantheon, is said to have been created by the fire of Ra’s eye; occasionally, Sekhmet, of note, is described as the wife or mother of Ra, depending; she is also said to have been the sister-wife of Ptah (Ѻ), and the mother of his son Nefer-Atem. She is sometimes portrayed as the sister form of the goddess Bast.
Sekhmet, aside from having “power of the waters”, whatever that means, also had the power to send out heat, as a fire-breathing snake, when she was in the form of a serpent on Ra’s head; she also was supposed to be able to shoot out “swift fiery darts” that would pierce the bodies of the enemy.
|A depiction of Hathor (left) and Sekhmet (right), the latter of which seems to be Sekhmet as a form of Hathor, or Hathor-Sekhmet, which was a synretism that occurred in "late dynastic times (Budge, 1904).|
Sekhmet, in late dynastic times (Budge, 1904), was syncretized with the goddess Hathor, to the effect that Hathor would become Sekhmet when in rage; the following is a synopsis:
“Hathor's strong solar connections are made obvious by the solar disk, supported by two tall cow horns and augmented by a uraeus, which she wears on her head. Among her different solar personae, she may be the wife, daughter or, occasionally, mother of Ra. As the fierce uraeus she protects her father with a burning heat; as the ‘golden one’ she accompanies him on his daily voyage across the sky; as the ‘eye of Ra’ she acts as his agent. But when the mild-mannered Hathor grows angry, she transforms into Sekhmet, the ‘powerful one’, an uncompromising, fire-breathing lioness armed with an arsenal of pestilence and plague. Sekhmet's destructive female anger — the burning anger of the uraeus — is put to good use as she protects Egypt's pharaohs. This fierce defense of the king, and her skill with the bow and arrow, cause her to become closely associated with the army so that Ramesses II, valiantly fighting his solo battle at Kadesh, might claim to be ‘like Seth great-of-strength; like Sekhmet in the moment of her rage’.”— Joyce Tyldesley (2010), The Penguin Book of Myths and Legends (§: Sekhmet and the Destruction of Mankind, pg. #)
|A depiction (Ѻ) of Sekhmet killing the wicked humans, with the flames from her mouth, the flames being the metaphor of the destructive heat of the sun, in a period of too much sunlight, too little rain or water.|
See main: Destruction of mankindSekhmet, famously, was the goddess sent to destroy humankind for their sins against the gods; the following is a recent synopsis of this myth:
“The most famous myth in which Sekhmet plays a part was that of the destruction of mankind. In the primordial past, when Ra ruled over the creation, mankind began to act out against the gods. Their behavior became very bad, and they forgot to care for the gods' temples. Ra became incensed over this behavior, and summoned his daughter, his Eye, Sekhmet. ‘Sekhmet’, Ra said ‘I wish you to go down to earth and teach mankind a lesson. I want them to cease their ill behavior and return to worship of the gods.’ Sekhmet nodded, and took off for earth. As one of Ra's eyes, she brought with her the fire of the sun, scorching the earth as she passed by. She began burning mankind and all his works, destroying everything as she passed. This continued for some time, until Ra became worried that Sekhmet would annihilate all of creation. Ra summoned Thoth to his side, to ask for his counsel. ‘Thoth, what can I do to stop Sekhmet from destroying mankind completely?’ Ra asked. ‘She is so fierce and free with her fire that I fear there will be nothing left.’ Thoth answered, ‘I have an idea’. Thoth went to earth, and crafted a lake filled with blood and beer. He lured Sekhmet to the lake, and watched as she began to drink. As she drank the lake down, she became drunk and sleepy, eventually falling into a deep sleep. Thoth summoned Ra, and together they returned Sekhmet to the heavens. Thus, mankind was saved from destruction.”— Michael Starsheen (2018), Tales of Egyptian Gods (pg. 132)
Osiris and storm
Sekhmet, in another myth, saved Osiris on the night of “some great storm” that hit Egypt; this reads as follows:
“Oh Hapi, great one [flood prince] of the sky, in your name of ‘the sky is safe’, may you grant that I have power over water like Sekhmet who saved Osiris on that night of the storm. Behold, the elders who are before the throne of abundance have sent me to just as that august god whose name they do not know sent them, and they send me likewise. My nostrils are opened in Busiris, I rest in Heliopolis, my house is what Seshat (Ѻ) built form me, Khnum stand up for me on his battlements. In the sky comes with the north wind, I will dwell in the south; if the sky comes with the south wind, I will dwell in the north; if the sky comes with the west wind, I will dwell in the east; if the sky comes with the east wind, I will dwell in the west. I will pull the skin of my nostrils, I will open up at the place where I desire to be.”— Anon (c.1375BC), “§57: Chapter for Breathing Air and Having Power of Water in God’s Domain”, Egyptian Book of the Dead, Theban recension (translator: Raymond Faulkner) 
“Ra crowned Osiris with the atef-crown in the Heliopolitan Nome, but the crown's powerful heat was such that it caused the new king to fall ill; its effects were so long lasting that after the ceremony, Ra found Osiris sitting in his house, his face all swollen. It was an inauspicious start to his reign, but Osiris quickly gained the reputation of being a great and benevolent king; indeed, he was well prepared for the job, having served as vizier, chief priest of Heliopolis and royal herald before inheriting the crown. And, standing 8 cubits, 6 palms and 3 fingers tall (about 4.7m or 15.4ft), he could certainly intimidate any enemies on the battlefield. His reign is described as a time of prosperity, when all resources were well controlled and the land was stable. Life was good, the disordered waters of Nun were kept at bay, the cold north wind blew (something particularly longed for in the fierce Egyptian heat) and animals procreated. Conspirators were crushed and Osiris was respected among the gods. In fact, the only significant problem faced by Osiris during his early reign happened when, one night, a storm hit Egypt and the goddess Sekhmet had to save him using her power over water.”— Garry Shaw (2014), The Egyptian Myths 
“In later legend, according to Diodorus (c.30BC) and Plutarch (100AD), the establishment of various social structures and customs was attributed to Osiris during his reign. Plutarch relates how, as king, he taught the Egyptians how to cultivate the land; he also gave them laws and taught them to honor he gods. Osiris, according to Diodorus, did many good deeds for the social life of mankind, for a start, by making them give up cannibalism, since Isis had discovered wheat and barley, they took up eating these instead of each other. Isis also established laws, while Osiris built temples to his parents and other gods at Thebes. Both deities honored those who advanced who nurtured the arts and made technological advances. One advance in particular was the development of copper tools, which helped people to kill animals and conduct agricultural activities more effectively. Osiris, according to Diodorus, was the first to invent and taste wine [compare: Dionysus], and he took counsel with Thoth on every matter.”— Garry Shaw (2014), The Egyptian Myths 
1. Faulkner, Raymond. (1972). The Egyptian Book of the Dead: the Book of Coming Forth by Day: Complete Papyrus of Ani, Featuring Integrated Text and Full-Color Images (translator: Ogden Goelet; Preface: Carol Andrews; Introduction: Daniel Gunther; Foreword: James Wasserman) (Amz) (§57, pg. 120). Chronicle Books, 2015.
2. Shaw, Garry J. (2014). The Egyptian Myths: a Guide to the Ancient Gods and Legends (pg. #). Thames & Hudson.
3. Budge, Wallis. (1904). The Gods of the Egyptians, Volume One (§16: The Great Triad of Memphis: Ptah, Sekhet, and I-Em-Hetep, pgs. 500-25). Dover, 1969.
● Shoup, John A. (2017). The Nile: an Encyclopedia of Geography, History, and Culture (Sekhmet, pg. 122). ABC Clio.
● Sekhmet – Wikipedia.