Each player has a deck of 51 cards, and each deck starts with your champion card in play. The aim of the game is to reduce your opponent's champion to 0 HP.
Resources are drawn every turn and they pass on to the next turn if they are not spent.
This makes the game a little snowbally, if you're not careful your opponent can gain a significant lead against you but there are things that can mitigate this lead.
A lot of the cards have conditional effects and achieving these effects allow you to either deal extra damage or gain more resources.
The Meritus (Martial) deck has the most staying power and your champion gains abilities from the equipment he wields. Various cards give him extra attacks and damage.
The Sortis (Magical) deck is very feast or famine, players either love it or hate it. This deck keeps very few cards (if any) in play and relies entirely on spells to keep itself going, the high risk high reward style can be tricky to get used to but it is extremely satisfying to pull off.
The Divitiae (Mechanical) deck uses bots to get everything done, constructs can be recycled from the hand to get you bonus resources but forces you to make the most of what you have left. It has some high defence cards that help you build up your front line and then wears you down with strong attacks and upgraded cards.
The Diogeni (Natural) deck is reliant on plants and animals to win the game. Plants give you greater resources to use over a long period of time which allows you to build up and use your high cost cards, crushing your opponent if they allow the game to go on for too long.