Head over to the Imgur Album where you can see all the cards linked to this one. These cards were designed about two weeks before League of Evil were released.
It includes 12 upgraded minions and 16 spells. One for each class and a few neutral ones. While some of the Concoctions have a class attached to them, any class can get them and play them. Like you can play a Warrior Deck and get the Priest themed Concoction.
Not all of these are intended to be so good to be viable in any meta. They are just intended to a game more flavourful and a little less static.
I've posted some thoughts on my reasonings but if you think any of the cards are overpowered or undertuned. Feel free to comment and maybe post your thoughts on if and which of the combinations are too bad or too good.
Ever wondered if a deck filled with only a single race works as a deck? A Warrior deck with only Orcs or a Rogue deck with only Gnolls. Check out some of the most "Race(ist) Decks"