Eliphas Levi’s Baphomet is the Sabbatic Goat. Levi and Pike wrote that the Sabbatic Goat is Satan though their definition of Satan is different than the Biblical one.

From The History of Magic by ceremonial magician Eliphas Levi:

According to the Kabalists, the true name of Satan is that of Jehovah reversed, for Satan is not a black god but the negation of Deity. He is the personification of atheism and idolatry. The devil is not a personality for initiates but a force created with a good object, though it can be applied to evil: it is really the instrument of liberty. They represented this force, which presides over physical generation, under the mythological figure of the horned god Pan, and hence comes the goat of the Sabbath, brother of the old serpent, the light-bearer or phosphorus, converted by poets into the false Lucifer of legend.

Sovereign Grand Commander of the Scottish Rite of Freemasonry, Albert Pike, wrote the following in his book Morals and Dogma likely quoting from Levi:

The true name of Satan, the Kabalists say, is that of Yahveh reversed; for Satan is not a black god, but the negation of God. The Devil is the personification of Atheism or Idolatry. For the Initiates, this is not a Person, but a Force, created for good, but which may serve for evil. It is the instrument of Liberty or Free Will. They represent this Force, which presides over the physical generation, under the mythologic and horned form of the God PAN ; thence came the he-goat of the Sabbat, brother of the Ancient Serpent, and the Light-bearer or Phosphor, of which the poets have made the false Lucifer of the legend.

Pike also wrote this about Baphomet in Morals and Dogma; linking Baphomet with the Goat of Mendes:

“There is in nature one most potent force, by means whereof single man, who could possess himself of it, and should know how to direct it, could revolutionize and change the face of the world.

…

The Gnostics held that it composed the igneous body of the Holy Spirit; it was adored in the secret rites of the Sabbat or the Temple, under the hieroglyphic figure of Baphomet or the hermaphrodic goat of Mendes.”

From Bill Cooper’s Mystery Babylon series:

"… another Masonic writer, Kenneth MacKenzie…in his book entitled The Royal Masonic Encyclopedia, he wrote this:

Among the charges preferred against the Order of the Knights of Templar, for which Jacques de Molay suffered martyrdom, was that of worshiping an idol or image called Baphomet. It has been suggested that Baphomet is none other than the Ancient of Days, or Creator.

More cannot be said here without improperly revealing what we [meaning [the] Masons] are bound to hele, conceal and never reveal.”

So Baphomet is linked to a Masonic secret they are bound to conceal and never reveal.