Also called the Cross of Saint Peter or the Petrine Cross, the inverted cross is simultaneously an anti-Christian symbol, and a decidedly Catholic one.
In The Martyrdom of Peter, found in the Acts of Peter (an apocryphal text dating to 200 AD), St. Peter requests to be crucified upside down out of humility toward Jesus. For many Catholics, it remains a symbol of humility before the Son of God for this reason. The Pope, deemed St. Peter’s successor as Bishop of Rome, and the rest of the Papacy sometimes use symbols of St. Peter – including the inverted cross – to represent their organization.
Contemporary religious dissidents have since adopted the symbol as their own.
For Satanists interested in using the Inverted Cross to blaspheme, it is best to use a crucifix with the likeness of Jesus, so as not to draw parallels with St. Peter.