An upside-down crucifix is also a symbol embraced by Satanists. That confuses some people as it is seen as the Petrine Cross or "The Cross of St. Peter" since, according to Origin of Alexandria, Simon Peter was crucified upside down. However, turning a symbol like a cross upside-down is symbolic on it's own and the interpretation of doing so differs among Catholics and Satanists.
In Alchemy, the Leviathan's cross is a symbol for sulfur, which is one the three essential elements of nature.
In Asia, its name is the Brimstone Symbol.
The association with the Leviathan makes it a symbol of depth and surfacing. The multiple crossroads of two crosses can be interpreted as a sign of free choice, it can also be seen as a stroke-through "equal-to" (=) to show that every person has their own life.
Sulfur (“Leviathan Cross”) A symbol for the alchemical element Sulfur, (Brimstone) which is spiritually analogous to the human soul. Alchemically, sulfur has the qualities of masculine, hot and dry. Combined with Mercury (feminine, cool and moist), the pair were considered the parents of all metals.
Alchemical drawings often portray Sulfur as the sun. (In some views, sulfur and salt are the parents of Mercury) The symbol of sulfur is often used as an identifying symbol by Satanists, due to sulfur’s historical asociation with the devil.
This glyph is often referred to incorrectly as the “pontifical cross of Satan” by Christian tract writers, due to its adoption as an emblem of Satanism by Anton LaVey in the 1960s. The emblem has no history as a symbol of Satanism outside of LaVey’s usage, and the attribution is most likely a product of anti-Catholic sentiment, as it is often compared in this context to the Catholic Pontifical Cross. A more common symbol for sulfur is a fire triangle surmounting a cross of earth.
The Leviathan Cross was created by The Knights Templar. The symbol was then adopted by Anton LaVey, founder of the Church of Satan. Previous associations with the cross and Satanic foundations are unable to be identified.