Snurgle, a 11th level Necromancer, uses the Magic Jar spell to possess the local parish priest, Father Benedict, trapping poor Benedict's soul in an ornate reliquary.
Your body falls into a catatonic state (…) your soul moves into the target's body, and the target's soul becomes trapped
Snurgle's aunt, the witch Emalia (a fifth level wizard), is unaware of these proceedings and tries to contact Snurgle with a Sending spell, to remind him to bring her some blood, bone dust, and rotting flesh when he comes to visit next time.
What happens?
Bonus questions: What happens if Emalia tries to contact Benedict? What happens if the wizard Waldemar visits the parish to obtain some holy water, meets the possessed Benedict without knowing him beforehand or realizing he is possessed, and later tries to contact him with Sending?
Best Answer
Depends on the answer to 2 questions, Likely a DM decision:
The Spell description for Sending states (emphasis mine):
(I'm assuming Emalia is targetting Snurgle, it just says "him" but Snurgle is a relative while Benedict may not be. Totally read this question wrong at first.)
Question 1: Who or What is Auntie Emalia targeting?
and she's attempting to reach "Snurgle"
A soul may or may not be considered a creature. (See Can a ghost or other incorporeal creature be polymorphed? on a ghost being a creature, the differences between a ghost and a soul may need to be settled)
Question 2: Are we familiar to Auntie Snargle? (The caster attempting to target Snurgle, not Benedict) How do we define familiarity in 5e? Can't say I've seen a definition in a rule book yet (in this context, we're not talking about wizard/warlock familiar), but a dictionary defines familiar as:
Which may refer to their physical appearances, though I'd lean more toward the intimate knowledge of history and shared memories etc, which would include more than knowing what they look like. Familiar friends can become unfamiliar over time for example, both in how they act and look.