Seeing the explanation/walkthrough at this point seems to be quite lacking I figured I would start a guide for people unfamiliar with cardgames.
Basically there are 3 boards, each board has towers (one is yours, one is the enemies) and you need to destroy eachothers. To do this, there are heroes (5 each) that battle each other, using anything from special cards, to grunts/creeps, to healing cards or specialty cards.
When you first start this game you will have two example decks (a set of cards) and be able to play two tutorial games against the AI/bot.
You will also receive 10 "Call to Arms" packs of cards, which contain 10 cards each. Open them and start building your own deck!
Solo, Social, Casual or Expert?
The game lets you choose the following game modes.
The aforementioned bot games.
You can tell your friends, Steam groups here that you are looking to play or directly invite a friend. You can even start your own tournament!
You can matchmake against people of your skill level, start a casual constructed game or a phantom draft.
Here you can play to win rewards, a 5 win series will net you 3 (?) and 2 decks!
The Game Itself
When you play the game, you've 3 boards.
Building a Deck!
When you buy the deck, you get 10 unopened packs. You can open these and start building your own decks. Alternatively you can buy or trade specific cards through Steam.
It is recommended to have your deck make sense and to keep your decks balanced. For example, having black cards in your deck does not make sense if you don't have any black heroes. You can only play cards on a lane after all if you've a hero on the board, and it has to be the same color.
It's also advisable to keep them balanced, each card comes with a number that shows the amount of mana you need to play the card, so if your deck for example is stacked with cards requiring 7 mana you won't be able to play any cards for the first six rounds.
There is a counter that helps you determine the balance per round, on the right side with numbers from 1 to 8+.