Hmm... in my campaign I have strayed from canon... But still the GC is always charming...
HEY, MY PLAYERS, DON'T READ THIS!! [points 1 and 2 are out of topic, you can skip right to 3 or even 5]
1) IMC, GC has STATS... well. havine a divine rank greater than 16 and some unique abilities still leaves him very very far away from the province of PCs. But, I always use stats because they make me feel I am not cheating/manipulating things (it's just a kind of playing).Ηe has 5 levels in a swordsman school, 10 charismatic, 3 smart, 1 fast and 20 acolyte

.
[are you still alive or died from shock?

) - we used a strange mixture of systems, resulting in him having many divine spells, a swashbuckling finesse with parry/riposte/slip and other Swashbuckling Adventures broken and renerfed things

, as well as appearence above average/dangerous beauty (some feats of SBA).
2) Strangely, no outsider hd (IMC he is a "fiend" regarding the few people who know him, but in reality, he is an agent of the Mists. Actually something like an avatar of the mists. A child that has its own schemes, and manipulates history to create interesting situations, in a vain attempt to feel a real sentiment - always keeping, though, this relaxed and charming attitude).
Of course, he's an acolyte of Mists - and himself.
3)I was influenced from Masque's of the Red Death Maestro to create some parts of the personality and tactics of Gentleman Caller. While in fact he needed only a couple of special divine powers to accomodate for the myriad abilities of Maestro (after all, reaching +120 bluff and +85 diplomacy is enough for most of them), it was mostly a roleplaying attitude and approach of manipulating people and torturing them that affected mostly the result.
4) Ok, we are getting into topic now: the first time the players learned something related to GC was when Gabrielle Aderre explained them her version of the history of Malocchio Aderre. That was their first contact with "a fiend who is Malocchio's father". After a very impressive moment with Malocchio Aderre (where he tried to erase the memories of their discussion with this mother from their heads, with not exactly 100% success) they continued their travels with the carnival (yes, they used carnival to travel safety back to their home - after all, they were almost outsiders and 100% lost) until they show a strange scheme failing (the adventure in the end of Carnival where there is a confrontation with Gentleman Caller).
They saw Gentleman Caller from afar, in his relaxed tone, toying with Isolde, but still having failed his plan. They were upset he disappeared. Discussion with Isolde left them with "there are some things you are not ready to know - you have to understand some other things about this world first". In this encounter, he was referred to as a gentleman... As far as I remember, the fact that he was Malocchio's father wasn't yet reveiled.
Their history brought them to ancient prophecies, trying to face the schemes of Malocchio. Their contacts very very slowly reveiled them the truth and the connection of this "strange Gentleman" to Malocchio's father, as well as the fact that he has some relations to the Mists. By this point, he was still an untouched mystery and a threat...
It took many months to reach the point of the campaign where the players caught really the attention of Gentleman Caller, with their efforts to spoil Malocchio's schemes. He started toying. A woman (one of the characters' ex lover and also a girl another character also liked) was found horribly murdered, having left created a pistol, and blackpowder (which they investigated, to learn that some of her own bones were used). Investigating the inside of the pistol (with some very clever ideas of them), they saw there was a drawing there, depecting an old woman, some insect-like monsters and ice. They recognized only the monsters (another element of the campaign - some outside force that had allied with Malocchio in his apocalyptic schemes). They found out also, that a charming gentleman with a foreign accent was seen with the lady during the last days. One of the players/characters imagined the relation (even though months have passed)... which was still unsure.
One month later (slightly more in in game time), they were on a ship to a long voyage, where they were caught in a sudden but horrible maelstorm, after having won a great victory over these insect-like monsters. As a cutscene (for which the characters are not aware), I described them somewhere among the clouds a gentleman and Malocchio having an interesting discussion, revealing that Malocchio was fed up with them, calling GC for the first time to act against them, while GC had some plans of his own - it was the second time I described to them GC, this time even more relaxed and gentleman... This convinced the players about GCs involvement, but the characters were still just suspecting it.
In the following sessions, they made some great discoveries in icy Antarctica (where the malestorm had left them). They found the old woman and her relation to the monsters. And the ice. They also learned a bit more about GCs relation to the Mists - actually that he was some kind of agent of them. But still his motives were strange (the players - don't ask me why, it's a long story, KNEW that the current schemes of Malocchio were not in the liking of the Mists). They were confused.
It took not long for them (in their trip, leaving Atarctica) to learn that another of their friends (also a girl they had liked very much), disappeared. A man's eau de toilette could be smelled by the team's werewolf (I duck to avoid flying objects towards me). They were HORRIFIED. It was when in game they started to realize that a gentleman, possibly (probably off game) the same gentleman they had encountered a long ago was chasing after their loved persons.
They found the girl
- and found another clew of their travel. They actually started thinking of the possibility that GC actually was lefting them some clues in this gruesome manner! (having an ally who slaughters your loved persons is an unsettling idea).
They confirmed the validity of the clue soon after... and the went on to the far away land they were heading to. Where, among others, they found out one of the PCs' mother (actually it was one of the reasons they got there). They had just confirmed her location and crafted a plan to immobilize her without doing her much harm (yes, she was not the epitome of being helpful, actually she had stolen the magic abilities of her baby son through an untold ritual)... Only to found her in her dying graps, nailed to the ceiling... She told them it was GC and that even if they raised her, she had an oath with him... After a lot of effort they resulted in raising her, while still she could not help them against GC.
Now they were furious. I mean as PLAYERS. One of them still (months after the events) tells me by msn at times that he will KILL THE *()*() BASTARD....
.
Cut... even more revelations on the other part of the campaign. One of them: Malocchio, their greatest threat and enemy, was dead (actually, through the combined efforts of many players and alts, but still, for one of the players, it was then he learned that their greatest enemy was already dead!). Ok... now the field cleared: they had a clearest goal... Even though they had realized by now that they had not much hope in confronting GC... this part of the campaign was to end with them facing GC... (I had to leave to France for a year)
They saw him (playing with the head of the last friend of theirs he killed, but still using white towels to avoid having blood on his lovely pants). Some were very calm and discussing about it. Some other FURIOUS with him. Actually there were 3 characters (and a cohort, ready to die with here compatriots should they chose it):
1 - normally very trigger finger, but at this point very calm and waiting to see what will happen
2 - FURIOUS, she was ready to kill Gentleman, kept only by his calming smile, but still ready to shout horrible things on him
3 - she had realized what's happening. She carried a big part of the discussion, having realized that he was playing with them. She impressed GC.
What happened in the discussion? GC was really helpful. Actually he said they did very well, that he had confiance on them! That he had set up all this story from the beginning, but didn't know how it will turn up and all the small details and turns it took. That he was the one forcing them to adventuring by making Leon (another big story) a ghost. He actually said in the end...
I am your storyteller.
Character 2 protested. A strong advocate of free will, she couldn't accept it.
"you can die with one single WORD of mine"
And she died [actually it's the life and death power from deities and demigods, but the notion of dying without a single roll was something COMPLETELY alien for players who had played with me for years and knew my adherence to the rules]
Finally, they convinced smartly GC that it was not a good idea for the story for her to die now - there were dramatic choices to be done. It would be better for her to die a bit later. And he raised her with a word.
They feeled strangely. Player playing character 3 didn't imagine THAT much. He was asking about the "narrator" part afterwards. The fact that I hadn't a stat sheet in front of me (I had it close at hand, and memorized everything important) was confusing them a bit... Was GC their narrator? But, in the end... they know me... Bah... Probably not, I will have a sheet close by. Probably...
But still, this worked with my group. I played with the notion of confusing in/off game, being very very gentle and sure of myself, and also the notion that GC wasn't making rolls - which was, as I said very alien for my way of playing.
I would have done it differently with a group who doesn't know me.