The Proton Laser, sometimes nicknamed the "Tentacle" Laser. Is a weapon first introduced in Raiden III. Initially, it acted as a replacement and successor to the Plasma Laser from Raiden II, but it would later appear alongside its predecessor together in Raiden IV.
The Proton laser differs from its predecessor by the fact that it does not automatically lock-on to nearby enemies and bend in a way to resemble toothpaste (hence the predecessors' nickname). Instead, this laser fires a number of streams of a similar material that stretches out and slowly saps the health from any enemies it makes contact with, because of this behavior of the laser streams, they take on the appearance as though they were large tentacles from cephalopods (octopi and squids). The number of streams, as well as the thickness of each one, increases should the weapon be upgraded by acquiring a power-up.
A notable from the Proton laser's appearance in contrast to its predecessor is the fact that it the streams have a green outline rather than simply appearing as being completely purple. Because of this, in Raiden IV, to differentiate the two lasers from each other, the Proton laser's power-ups are green to avoid confusion.
The proton laser's stats are largely identical to its predecessor, with a long range and a somewhat low damage output. The biggest difference besides the tentacle-like behavior of the streams is the accuracy which proves to be slightly inferior to the plasma laser. Nevertheless, the Proton laser is still a good choice for tackling large menageries of enemies.