After posting Hiding Vampires In Plain Sight, I realized that I either had to explain away a vampire's odd traits with a mutant variant of Toxoplasma gondii (no easy task) or somehow keep people's mouths shut in such a way that no one, absolutely no one, could spill the beans. And so I come to Imperi.
Imperi are special vampires, composing a mere 1% of the vampire population, with the "power of blood." What this means dips into the natural symbolism of magic in my world(s); basically, because blood symbolizes life for vampires, certain vampires can not only extract essence from blood but gain power over whoever the blood came from upon doing so.
These vampires are used to keep vampires in check and ensure their secrecy stays secret, using their powers.
Now, Imperi are capable of doing just that, but that arises the question, which I must answer so you must answer mine: What Are The Limits Of An Imperi's Power?
Proportionality-An Imperi's power over someone is directly proportional to the amount of blood they've taken from that person. After taking 1 liter of blood from someone, an Imperi can get them to act friendly when they feel otherwise, or begrudgingly do something (show them to a destination, give them a fair price for a product, be honest with them when they want to lie). After taking two liters from someone, an Imperi can make someone do something they wouldn't normally do, like they could if they knew one of that person's secrets or the person lost a bet. The extent of this power would likely cap out at doing something ridiculous and embarrassing in public, like jumping up on a table and doing a little song and dance. In order to gain total control over a human, an Imperi must consume an entire body's worth of blood from one individual and turn them into a vampire, which segues directly into....
Vampirism-When a human is exsanguinated (drained of blood), they must be 'refueled' within 24 hours or die (within that 24 hours, the victim, or 'husk,' is on the edge of life and death). What this means is that the person must have their lost blood replaced, and the consequences are simple: if the new blood is human, the victim will remain human, but if the new blood is vampire, the victim will be 'raised' as a vampire, Imprinted upon the vampire whose blood raised them.
However, this is problematic for Imperi; their 'power of blood' goes two ways, so raising a human as a vampire will not create a thrall under their total control but will rather give human and Imperi equal power over each other. Raising a human with another vampire's blood instead would instead give that vampire total control over the human. There is one exception; an ability, called Chtonic Chains, allows an Imperi to gain and retain total control over someone by raising them as a vampire, but this knowledge is now lost and finding it is signing your death warrant.
Two-way Street-As stated above, an Imperi's powers go both ways. This means that if a human were to take blood from an Imperi into their own bloodstream, they would gain power over that Imperi. This is how the human government controls Imperi; each and every Imperi is bound to a specially chosen human agent through their own blood, and this agent (called a 'Check') is tasked with keeping the Imperi on the straight and narrow, as well as serving as their donor (to increase their power over their assigned Imperi).
Ambrosius Legacy-An Imperi's powers stem from the legendary Ambrosius, a female mage of incredible power. Because of this, an Imperi's power has three important limitations:
a. An Imperi cannot compel someone to betray themselves (ie. act in a self-destructive way, such as by taking a fatal blow for an Imperi). By extension, an Imperi cannot use their influence to drive someone insane. This extends only to the things that someone absolutely will not do for anyone, so this limit can be worked around.
b. An Imperi cannot compel someone to harm or betray their loved ones.
c. An Imperi cannot compel someone to take a life, directly or indirectly. This means an Imperi cannot compel someone to commit suicide
- Based on Influence-An Imperi's powers are deeply symbolic; taking blood from someone symbolizes taking part of that person into themselves, which gives them a kind of power over that person because if you understand someone, if you're connected to them, you therefore have power/influence over that individual.
Thus, an Imperi's powers can be relatively weak unless backed by other forms of influence, such as loyalty, legal authority, wealth, or force. However, these things also increase an Imperi's power over an individual. Example: since an Imperi has legal authority to use their powers on someone who finds out about vampires in order to keep them from blowing their secret, all they need to enforce this authority is to forge a connection, ie. take a drop of blood. Then, drawing off of the power of their superiors, they can bind that individual to not reveal the secret of vampires through word or deed (ie. in any possible way).
Loyalty and promises of money increases an Imperi's influence only slightly; with 2 liters of blood, an Imperi can make a loyal individual do something illegal, like breaking and entering to find evidence of something or to claim something valuable, while with the promise of good pay, an Imperi can cause someone to not turn them in, or aid their escape, or take the risk of grabbing something when they wouldn't otherwise, after authorities get involved. (The same goes for loyalty, which probably goes without saying.)
My question is, Are Imperi Balanced?
I'm asking because Imperi are, specifically, meant to be extremely powerful but limited in scope. It's not opinion-based. If I was asking if Imperi were a liability, that would be too story-based. However, I'm asking something much more specific, something specifically answerable. The human government would like to use Imperi to keep vampires in check, but they can't if they are too dangerous to keep alive. So, where do Imperi fit? 1 (too weak to be useful), 5 (powerful enough to be useful, but weak enough to be kept in check), and 10 (dang it boys, we've got another Cthulhu on our hands!).
Clarification on Vampirization:
Drawing off of Culyx's example, if Vampire A drained a human and replaced the lost blood within his blood, a new Vampire (B) would result. At this point, Vampire B has made Vampire A's blood his own, and thus by doing the same would create Vampire C, who would be Imprinted on B and not A.
Further Clarification: Yes, Imperi are supposed to keep vampires in check. No, their powers don't seem to concern vampires specifically. However, considering a vampire's 'blood weakness,' they are actually more susceptible. 1 liter from a vampire will give an Imperi as much power over them as 2 liters, and 2 liters is equal to 4 liters.
Thus, an Imperi only needs 2 liters of blood from a vampire to have almost total control.