The strategy is in the card management; how you use your cards, against whom, using them at the right time for full effect, combining them with challenges given by other players to make the turn even more challenging. Every player starts the game with 6 cards (1 Guardian and 5 random cards).
It is up to you how easy or difficult the game is to other players. The cards have challenges on them that you can use against other players to make their turn harder to do, which brings up the take that mechanic of the game. Every player may only use one of their cards against the active player, so choosing the right card is important
If you are too aggressive, you will run out of cards fast and you must either wait for your turn or pay points to get new cards. So, you must use your cards strategically to try and make the other players lose. If you want to win, you need to be smart about how and when to use your cards.
You not only have challenge cards, you also have an ability that you can use to help yourself or against another player. However, just like the Guardian card, you may only use your ability once per match.