Running the Caller as an antagonist

[SanahGrat]

So I recently started running a campaign centered around the Carnival. The idea is essentially the party travels as part of the carnival through the different domains, dealing a bit with the individual settings for some variety and given his personal connection to Isolde it made sense to make the Caller (or Gentleman Caller in older editions) the BBEG, with some Azalin related stuff going on in the background. Essentially while they travel through the Mist they end up running into the Caller time after time, sometime by pure chance, sometimes because he lured them to toy with the party and of course because Isolde is hunting him

As his true motives have always been shrouded in mystery I took some liberties with that. As far as I gathered he essentially travels the Mist to screw with people, sires some children and looks for a way to escape the Domains of Dread.

So here is what I came up with: The caller is gathering the children he has sired over the years, all of them showing some remarkable abilities. He also got his hands on the plans for the Apparatus and tries to rebuild it. Currently he is still looking for the Rod of Rastinon - his plan is to split the souls of his children into a "good" human half and an "evil" fiend half using the apparatus and using the very same to merge the fiend halves with himself, increasing his power with which he hopes to escape the mist.

Would love some feedback and suggestions

[Mephisto of the FoS]

So here is what I came up with: The caller is gathering the children he has sired over the years, all of them showing some remarkable abilities. He also got his hands on the plans for the Apparatus and tries to rebuild it. Currently he is still looking for the Rod of Rastinon - his plan is to split the souls of his children into a "good" human half and an "evil" fiend half using the apparatus and using the very same to merge the fiend halves with himself, increasing his power with which he hopes to escape the mist.

It isn't a bad concept. If I was a PC I would like playing an adventure that builds up and then reaches a climax.
For instance maybe the PC's encounter some of the children randomly, and then using the most evil of them as recurring villains, maybe even allying with The Beast of the Hills.
For instance they could encounter the Joungler as Ivanas bodyguard (and nothing more except seen as a goon not giving any clues to something else whatsoever) while adventuring in Borca, maybe helping Ivan in a plot against Ivana or vice versa.
The Gentelman Caller I believe should be behind the scenes most of the time, maybe he leads the PC's sometimes where he wants taking various desguises and maybe towards the end he joins the party as some upstart NPC or something and then they are betrayed or ubderstand that they have been helping the fiend all the time. I believe the horror that someone feels when something bad happens by their own actions is better.
Then in gathering the children I would play the children as unwilling subjects to that experiment as by merging with the fiend they will be non existing, probably a cambion with low self esteem like the Beast in the Hills may do it willingly with promises of beauty and power. Thus the GC could corrupt her into merging with him, shocking the PC's. I believe the last child he would try to get would be the imp as it is far too dangerous for him, maybe he uses the PC's to get it for him.

Also you will have to decide where the other children reside, for Sure there is one in the various islands of the Sea of Sorrows and the same applies for the Nocturnal Sea. Then the other's could be in more thematical domains. Maybe one in Pharasia another in Sri'Raji that they already have demon or outsider darklords. Another may be in Rokushima Táiyoo.

[alhoon]

Awesome concept and good luck.
Suggestions: Remember the GC is supposed to be steps ahead. Cunning and prescient with centuries of experience. How you would reflect that in his plans may not be easy, so I would suggest you give yourself some leeway. I.e. if the PCs arrive at X and the time isn't right, assume the GC has predicted that and is already away. Things like that.