Thanks for playing!
Later in the game you unlock Chaos Realm, where you face waves of random enemies until you die, and Campaign Mode, where you play through the scenarios in order and have to make do with the relics you find along the way. In the latter mode, you need to start from the beginning when you die. I don't think either mode is exactly what you're looking for, but they are more roguelike-ish experiences. I particularly enjoy Campaign Mode, myself!