Available to patrons through that site and for everyone else here the Character Compendium is a compilation of the four existing character packs into one book.
As monthly support results in a lot of stuff being out there, several fans have asked if we could get some of them merged into a single book, which seemed eminently reasonable.
This combines the Sooth Sayer, Character pack 2 (extra heroes), 3 (animal companions) and 4 (hired helpers) into a single volume.
Additionally, this seemed like a good time to revisit the rules based on feedback and additional play experience and tweak some things. Some hero skills were redone, but mostly it's fairly minor stuff to just make them work better.
In order to make it more exciting, I decided to add a bit of new content as well, so the package features 2 new hero types, 1 new animal companion and a new spell caster. This also means that the Sooth Sayer mechanics are basically the template for magician-type characters in the rules. Go forth and make many more.
If you just picked up all the original packs in the sale, you don't have to rush out and get this one. Get some mileage out of what you already have and then upgrade later. While we always try to make expansions support and work with each other, the rules will never rely on you owning a specific expansion pack.
If you are a "core rules only" kinda guy, make sure you have downloaded the most up to date version, especially if you haven't in a while. Some pretty substantial additions took place last year, including much-improved Wounding rules, the new Contract system and much more.