[quote=@Cu Chulainn]
Interested! So to clarify, we'll be playing as something similar to Demi-Servants, albeit with the possessed individual taking the forefront over the Heroic Spirit being utilized?
[/quote]

Basically Demi-Servants, yes. How much sentience your Eudaemon (i.e. your copy of the Heroic Spirit's data) has is up to you. It could be a full-on second personality, or its traits could merge with and influence the host, or it could outright take over the host's body, etc.. Whatever makes for a good story.