The Bubble Dragon is a Hardmode gun. It uses Hydro Charges to shoot erratically-moving bubbles. On collision with tiles or enemies (or simply after a delay of two to three seconds), these bubbles will split into multiple smaller bubbles. The smaller bubbles inflict 25% less damage and will despawn upon further collisions with tiles or enemies.
The Bubble Dragon has a 25% chance to drop from Nitori Kawashiro.