Was looking through the patchnotes of the 0.9.x series and this particular one seems to not actually be a thing in the current version…
“- CHANGE: Creatures can now manually cast Dark Ritual, Death Siphon, Reincarnation, and Sudden Death on themselves.”
My Abyss Banshee is not allowed to self-target with its Siphon, and creatures that i’ve put Ritual or Reincarnation onto cannot self-target either. Neither of my saves has Sudden Death yet so i can’t be sure about that one.