how can i make something similar Dark Souls Multiplayer

[folfd]

Im DMing 3 differents groups each other with a different adventure Kingmaker, Rise Runelords and Skull and Shackles months ago i finish a 4th campaign, Curse Crimson Throne, all of them using pathfinder 2e mechanics

So learning about the Lore of these adventures I discover some of them have a little Connection,

Spoiler:

Kazavon and his 7 relics

also i discover the theory of certain wizard who makes and interesting theory

Spoiler:

Nafzu Dilatru and his theory about the killers pattern

an strange force who push people to kill. So i was thinking in use this little connection as the strange force and mastermind in the shadows behind all the adventures, and wanna make the differents groups can help each other or at least join forces against this strange and powerful force but without interfere in the adventure of the others groups, or at least dont make a huge interfere, something like Dark souls via messages where they can give others Tips about an monster or in a situation if they are stuck.

This what happens in my campaigns:

In curse of crimson throne:

the heroes destroyed the crown of fangs and defeated Kazavon, but begin to investigate the blood pool of ileosa, so they discover about Azlanist, and eventually they found her and defeated too

Rise of runelords:

Since they asked me playing in pathfinder 2e, i changed a bit the lore, beign Azlanist the first runelord in surge, and new thassilion arises. the events of serpent skull already happen but certain character said no and comeback to the place where lives,

Spoiler:

Ameiko rejected beign the new queen on Tian Xia and comeback to Sandpoint

and the group has the notes of the wizard

Spoiler:

Rafza Dilatru

Kingmaker:

the group has the baronny and they have began relationships with Taldor, and new thassilion, also they started the Council of the Greenbelt which unifies a lot of Countries.

Skull and Shackle:

They are free captain now, and conquer the castle, but one of the players want the throne of nalt, which is one of the relics and destroy it.

So plot goes like this

*Alert of great Spoilers:

in the adventures Since eventually each group will have contact with one or two of the relics, and probably sold them or destroyed them, i wanna make the force who is ploting behind each campaign, he wants take possesion of Kazavon body where it can influence Belkzen and even the same Zon Khuton, have and inmmortal body its a extra, to achieve his goal, he will rise karzoug again so he can take control of the rune magic and the Oliphant, in the Kingmaker he is the whispering voice it makes the nymph attack the players and its the voice making Pitax expanding to the greenbelt and makes Armag believe he is the champion of Gorum and of course increasing the inestability in Brevoy, so in the end everyone will fight and who ever win, the force will control it and have access to a lot ancient artifacts and establishing a powerfull kingdom with an inmmortal it will make an immortal empire, and controlling the greenbelt he can expand his influence to first world and even the eldest, and in skull and shackles he needs the throne of nalt so he can recover kazavon body and controlling the shackles he will take control of the seas