Campaign Idea - Forest of Fiends

Okay, so I'm still playing around with ideas for my campaign after this one.  I'd like to do something different.  Different not only from what I've done before but also what my gaming group comrades have run for us.  One type we haven't done is the classic sandbox: the GM draws up a map, populates it with locations and encounters, and unleashes the players on it.

A little while back I read a great sandbox idea over at The Wandering Gamist meant to be done in the Adventurer, Conqueror, King System (ACKS).  It's a take on the idea of a "lost continent" ripe for exploration.  I liked that general concept so I'm doing some prototyping with ideas to see if I can make something come together.  The rules set is as yet undecided, partly so as to not limit my thinking, but also because I'd like to offer the players a couple options and let them choose.  I'm generally thinking "not Pathfinder"--because that's our go-to set and this campaign is meant to be a break from the usual--but I'll leave it up to them.  I'm grabbing the deities from the old Forgotten Realms setting because I've always liked them and because I'm not motivated to do an entire pantheon from scratch.  The working title is "Forest of Fiends" because it will feature a lot of chaos, demons, and jungle.


Background

A thousand years ago the Empire of Pra-Kryush ruled a mighty continent and made war to conquer lands far across the sea.  Their power rested on a blood-soaked alliance with the vile Marilith Queens.  With the aid of demon generals and titanic warbeasts supplied by the queens, the armies of the empire conquered lands far and wide. There they built temples to the Queens where the blood of victims filled the sacrificial basins and all knelt before the abyss.

But there came a time when the Queens' lust for conquest and blood could not be sated and they turned on their allies in Pra-Kryush.  Ravenous demonic things poured from the temples and the empire fell into chaos and fire.  The conquered lands seized the opportunity and  rose up with the help of their True Gods and threw off the yoke of the empire. These liberated lands renamed themselves the Holy Realms.  But the heartland of Pra-Kryush, across the wide ocean, was declared anathema: travel there was forbidden and any who delved into knowledge of summonings, demonology, necromancy, and other hell-arts were burnt at the stake.

Seven years ago Warpriest Chazan, the greatest priest of the god Torm, proclaimed a vision from his god: that the time had come to cleanse Pra-Kryush and establish the light of the True Gods there.  The temples of Tyr and Ilmater, the other two members of The Radiant Triad, joined their ally immediately.  The kings and queens of the Holy Realms quickly responded, both from religious fervor and an unparalleled opportunity to acquire land and treasure.  The kingdoms and temples sent various expeditions but almost all failed for one reason or another.  Pra-Kryush is still a place of doom.

The adventure begins in the town of Tymoris on the riverine island of Light of Fortune, where a sprawling temple-casino of Tymora anchors a ramshackle boomtown awash in fortune-seekers of every stripe.  Crusaders, exiles, colonists, pilgrims, pirates, and desperados all rub elbows in the streets and taverns.   Light of Fortune is located in the delta of a massive river dubbed the Hellflow.  All manner of fiendish creatures swim in it, just waiting for prey.  Rumors say the waters boil up from a cave in a fire-mountain, bringing the creatures up from the depths.  Luckily they generally avoid salt water so ships from the Holy Realms can usually get to and from the seaward side of the island unmolested.

 A forgotten people built a town on the island which scholars claim was called Tymoris.  The island is rocky, with only scrubby grass and stunted trees on the upper surfaces.   Fortunately, the original inhabitants built a reservoir and equipped it with a magical fountain to provide drinking water.  Channels and piping, now restored, carry water to several other small fountains throughout the town.  Despite the inflow of colonists and fortune seekers there are still a number of empty houses on the island, although all buildings legally belong to the Council of the Triad who act on behalf of the monarchs of the Holy Realms.   The days are warm and sunny with occasional light showers sweeping in from the sea, but in a few weeks the monsoon rains will arrive.

The game begins as the ship on which the party took passage approaches the town docks.  The captain of the Brightwave, an elder human named Tio Manzzada, has made the long passage seven times already and regaled the characters during the trip with rumors and stories--some of which may actually be true.

Features of the Campaign

The adventures will include much adventuring in the wild jungles, but also many "dungeon" type locations.  Encounters with demonic creatures, fey abominations, and natural creatures of the jungle will be frequent.  There will be significant political interactions with factions from the Holy Realms, particularly the temples.  There may be some travel by sea along the coast (this is a sandbox type campaign).  Travel back to the Holy Lands is not expected as the focus will be on exploration of Pra-Kryush--and dying a lot.

Pra-Kryush is a tropical jungle land.  Few maps remain from the old days, as most were burnt with their heretic owners to protect the faithful.  Even now there are only partial maps and navigators logs providing any information and even them mostly only what lies on the coast.  Old songs tell of a grand Cloud Plateau far inland, homeland of the inscrutable fey, who are as evil as the demons who presumably still prowl the lowland jungles.