You can see an ultrashort overview of the continent Aventuria in the quickstart. I will mention here that the universe, according to the arcane theories of learned mages, consists of seven spheres of which the third one is the one containing the world. The gods live in Alveran which is the fifth sphere while the demons belong in the seventh sphere. The usual belief is the belief in the Twelve Gods. While these gods only very rarely interfere in the third sphere directly, the third sphere contains an amount of their karmic energy that ordained followers, the Blessed Ones, can tap into to work miracles. Of the Twelve Travia, the Goddess of hearth, house, family, will play an important role in this campaign. The opposing force to the twelve is the thirteenth god, the nameless one. Where the twelve have domains that cover everything that is good, he covets pure power and obtains it by manipulation, bullying, hatred etc. He too has ordained followers (Blessed Ones would be a strange term in this case) who work their evil deeds secretively because in Aventuria there is no mercy for followers of the nameless one, the rat child, the prince of rats or by whatever name he is called.
The Simyala campaign starts in 1022 BF (Bosparan's Fall). It came out after two epic campaigns and your characters would know at least in outline, what were the results of thos.
The Phileasson saga
Two captains from Thorwal, Asleif 'Foggwulf' Phileasson and Beorn 'The Blinder' Asgrimmson, compete for the title 'King of the Seas'. They have to circumnavigate the world in 80 weeks and do twelve works on the way. They each have a crew and are accompanied by a Blessed One of Travia who tells them their tasks. It seems unlikely that your PCs would know much about this event, if indeed they even heard of it at all but for the players it would be good to know that Phileasson is overall the good guy and Beorn the bad guy. It is rumoured that Beorn in the end offered his life somehow but no more of this.
The seven marked ones campaign
In this heavyweight campaign, an old mage named Borbarad, banned into a globule some 500 years ago, is brought back and creates pacts with no less than 7 archdemons. He brings large parts of Aventuria under his control and can only at great cost eventually be banned again, in a lesser globule this time. His dominion fell to seven successors, a few of which have been dealt with at this time. Only in the east of the Middle Realm are remaining Shadow Lands. Many people have lost family members etc during all the upheavals and it is near certain that your PCs have general knowledge of all these events, however they are mostly irrelevant for our campaign.