He's not a Chosen. He rejected Mystra (see the relevant scenes in my Sage of Shadowdale trilogy). He is an (unwitting and unwilling) Weave anchor.
#realmslore
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Bits, Bytes, and Bourbon
@DecryptedTech
@TheEdVerse
Something I have always wondered. How does Manshoon (and his seemingly endless supply of clones) remain a chosen of Mystra? How does each clone keep that, especially the one that became a Vampire?