The Blaster is an enemy that appears exclusively in Kingdom Hearts Birth by Sleep. These enemies appear in Deep Space, and are merely laser guns embedded into the walls of the Grand Councilwoman's spaceship, guarding the zero-gravity control of the ship. They will open fire if the player gets too close to them, otherwise they will remain inactive.
If you use Block at the right time, you can reflect the blasts back to the Blaster, which will take damage. They will not attack Aqua, due to her alliance with the Grand Councilwoman.