Ever heard that the God of the Old Testament is not the same God in the New testament. Well it is not new news, it was old news and our early church fathers had to defend the truth regarding this false teaching.
Marcionism was a heresy that taught there were two gods, the stern creator God of the Old Testament who was really a demon, and the merciful God of the New Testament.
Marcion rejected the Old Testament entirely, keeping only ten of Paul’s letter and an expurgated Luke and Acts.
Marcionism was denounced by its opponents as heresy, and written against, notably by Tertullian, in a five-book treatise Adversus Marcionem, written about 208. Marcion’s writings are lost, though they were widely read and numerous manuscripts must have existed.