Here is my first draft:
Arcanaloth
Let me know what you think. I am completely open to making adustments. All spells are hyperlinked to the LevelUp A5e.Tools (which is a pretty awesome resource) for ease of use. Also, I still need to check the CR and do some fine tuning.
Finally,
@Morrus: when making this monster I noticed something a bit strange about the spell
finger of death. The LevelUp version doesn't allow a saving throw, but the O5e version does. Was this intentional or an omission? They are otherwise exactly the same, but that seems like a fairly significant difference IMO.