Poppycock. Celsus' treatise is named The True Word, not Contra Celsum, which is the 3rd-century theologian Origen's rebuttal. The entire book was contained in Origen's document. It was saved by 13th-century copyists, by the way. (So much for churchmen hiding stuff...)

As for Pantera's paternity, it is part of a lewd legionnaire marching song. Mary was a prostitue who got pregnant by the brave Roman, and was kicked out of her home by her father, according to the song.

In other words, the Pantera legend is just crude polemical anti-Christian propaganda. Is either ChatGPT or you sure that you want to repeat it?