I'll just say two things 75% it's a hawkin card and 20% its Brook or some Gifter so don't get annoyed when your head canon of fight with death gets destroyed. Nowhere in OP is it mentioned that there is this entity so it would be a bigger asspull, though there can be one thing that this is Enma soul.
Also there is specific mention of drug effect before this scene so it might be just all happening in his mind where Enma is taking control as it has happened before physically now its mentally and this is how Enma would get conquered ny Zoro. He conquered it physically now its about mental.