How would these "vapourous gates" work? I understand their one-shot useage, but who has the capacity to create them?
As an incredibly talented temporal mage, I would suspect Argus has this kind of power, but it's sealed for the time being. (Correct?)
Perhaps Gaspar is the one who creates them - when the party members in an era have completed their task, Gaspar would realize this and could create a gate on demand.
Claado -
While I understand you don't want to give away all your secrets, something involving how the party travels through time is probably something everyone should be aware of. If it really involves something you want to keep under wraps for awhile, at least PM/IM someone and bounce it off them to make sure it won't be problematic.
Its not that I don't trust you or anything, its just that with as many people as we have participating in the project, we need to foster communication about these sort of issues before everyone starts writing too far and we realize there's going to be a conflict of ideas.