With respect to journeying to Havenhythe with some existing characters, could Malak be a potential candidate?
- He's a vampyre of (minor) significance from old content, and I don't think he's qualifies as "quest-locked" in the sense that he can't be used outside of the one quest he appears in (Desert Treasure)
- I would bet that his status in DT / presence in OSRS means that he carries a base level of familiarity to less story-focused players
- I imagine that, outside of altering the text in his initial encounter with you in DT, a role in Havenhythe's story wouldn't necessarily conflict with a role in DT, regardless of which order a player completes them both - assuming his personality wouldn't drastically change over the course of Havenhythe's story, I could see him tricking you into killing a rival no matter who you are to him
In terms of what I think could offer the story:
- he could fit a more abrasive/antagonistic role within your core team, or even fit as an independent party
- relatedly, if he's not Zamorakian he's at least Zamorak-adjacent, which isn't usually the case for an ally
- his presence can fit regardless of whether he was sent by Vanescula or acting purely out of his own interest
- he could offer knowledge/perspective on existing vampyre society in contrast to vampyres in Havenhythe/Vampyrium, both in terms of new info and info obtained within the myreque series
- he could eventually help bridge the gap between havenhythe and Myreque when the latter gets folded in as a requirement
- he's also somewhat of a blank slate at the moment, even as an existing character, so he could be moulded into whatever the story needs
I guess his current model is graphically outdated, but, idk, he could get a new human model built out of existing assets at the very least