Did Palpatine have Dark Side Adepts on Byss before RotJ?

Did he? Or did he start employing them only after his death over Endor?

He had them on there before I believe. It says they helped in subduing the population.

He had Adepts since the Empire began really.

Originally posted by Zenwolf
He had Adepts since the Empire began really.

Do you have a source for that?