Yes, you read that correctly. It is actually what John says in the book of Revelation. I am currently reading the book of Revelation for my devotions.
Here is Rev. 2:24 from the New American Standard Version of the Bible:
“But I say to you, the rest who are in Thyatira, who do not hold this teaching, who have not known the deep things of Satan, as they call them—I place no other burden on you.“
According to Gary Burge in his terrific work on John’s gospel, John likes to allow for double meanings at times.
It seems that the “deep things of Satan” could both be a sort of mockery, and it seems to describe a Gnostic-like (Gnosticism does not kick in this early, more of second century reality) idea of special knowledge for certain, select folks.
Either way, the deep things of Satan are unimpressive in light of the riches of the true gospel!