Inverted Cross

The inverted cross, also called the cross of St. Peter originally was a Christian symbol ... St. Petersburg Peter was crucified upside down of his own free will, not feeling worthy to die in the same way as Jesus Christ. 

Today, the inverted cross is often viewed as a symbol of satan, a sign of the rejection of Jesus and accepting opposing values.

The Church of Satan itself does not reject this symbol, however, due to its strong connection with Christian symbolism, it rather avoids it. On the other hand, he considers the Sigil of Baphomet to be the main symbol.