Like seriously especially when you read primary sources. Premodern Christians of all sects strongly believed in an active struggle between God and Satan - even freaking Martin Luther did in how he understood his rivalry with the papacy. For some reason modern Christianity became more monist - you just never see this side of things coming up anymore - and I think this is why many Christians in the 21st century in justifying how they view Satan as an extension of God's will seem to come across as autistic sociopaths.