The whole idea is building parties with different characters, equipment, and skills. Once you win they are done. There is some meta progression to unlock more characters, equipment and skills. It's a great game and the DLC just dropped.

What Darwin said, plus there is an endless mode, you can go till you actually lose. There are also modifiers you can mess with. Ie if a character dies in battle, they are gone. Or Limiting team size to 3 or even solo. Another is if you lose the fight, you're done. Currently trying my hand at the endless. I find it enjoyable while afking another game.