What is the game about?
The game is currently about a group of adventurers trying to defeat an evil demon.
What is Taint?
Taint is any physical or mental affliction that harms your character. Disease, evil powers, mental disorders, and acts of evil all give taint. Page 62 of Heroes of Horror explains the taint mechanics.
How will Taint fit into the campaign?
Taint will be used to inspire fear and dread in players. Where some creatures were lack luster because of an ability, they will be refitted for taint. Corruption can kill while depravity will drive one insane. How characters will deal with this is part of the experience.
Where are all the gods?
Dead. No true gods remain, only demigods or powerful beings like angels, demons, and the occasional dragon. Some say that there are old beings at the far end of our world but that they are mad and strange things.
Is the campaign serious?
To a degree. Keep your character from being silly, a joke here and there is okay but the world is very bad. Evil usually wins and good creatures are seldom born. The world is morally gray. Less knight saves princess from dragon and more bandit lord kills dragon then sells princess to highest bidder. Good exists but is rare and seldom survives. Also, no resurrection magic.
But I don't want my character to die!
Everywhere you go, there are shrines and altars devoted to dark things. Simply go there and use ancient unholy rites to raise your character. Think of them as "Magic Wish Shrines" only instead of a genie, you get to deal with dark depraved elder things which demand payment.