You can convert your Cubes into Bolts by visiting the THNDR Shop. If you don’t have enough Cubes, those can be purchased in the shop as well. For every 21 Cubes, you can receive 10,000 Bolts in exchange. Some larger Cube packages offer better deals with more Bolts.
Bolts can be utilized to engage in higher Duels, which significantly speeds up the levelling process.