Orcus’ lair actions from OotA still says:

“Orcus’s voice booms throughout the lair. His utterance causes one creature of his choice to be subjected to power word kill (save DC 23).”

Power Word Kill has no saving throw. It’s been years now, has there been no time to fix this? That's now in the queue!

— Jeremy Crawford (@JeremyECrawford) April 14, 2018