The Cross of St. Peter or Petrine Cross is an inverted Latin crosstraditionally used as a Christian symbol.
In Roman Catholicism the Petrine Cross is not seen as Satanic in any way. However, an inverted crucifix (a Latin cross with an artistic depiction of the crucified body of Christ upon it) is seen as immensely disrespectful, and could be used to represent Satanic forces. The distinction between a Cross of Peter and upturned Crucifix is sometimes obscured, leading to confusion about the acceptability of each symbol.
Even though its primarily not seen as evil, this symbol has become very popular within anti-religion groups and among some extreme metal musicians, notably black metal ones. In popular culture, including films such as Rosemary’s Baby, Exorcist: The Beginning and The Omen, Petrine Crosses are often displayed to represent Satan.
If it looks like a duck, walks like a duck, and talks like a duck…then it probably is a duck! JS