Rainbow Gun

The Rainbow Gun is a magic weapon found in the Hallowed Chest, which can be found in the Dungeon, and may be opened with the Hallowed Key. Firing the Rainbow Gun will consume 20 Mana, and fire a rainbow-like curving beam that deals continuous damage to any enemy that walks into it at a rate of approximately 5 "ticks" per second. The "rainbow" will persist for approximately 10 seconds before dissipating, or until another rainbow is fired; which will cause the first to fade.

The projectile will travel in a straight line before succumbing to gravity and curving downwards.
 * When firing 90 degrees, vertically, the beam will travel in a straight line for approximately 65 blocks before curving.
 * When firing 45 degrees, diagonally, the beam will travel in a straight line for approximately 4 blocks before curving, this is only because the length of the beam segments is approximately 3 blocks long.
 * When firing 0 degrees, horizontally, the beam will travel in a straight line for approximately 35 blocks before curving.

Tips

 * This weapon will pierce infinitely until it fades, and is a great weapon against enemies with multiple segments; such as The Destroyer, as it will damage each section simultaneously inflicting tremendous damage.
 * The rainbow gun is also exceptionally powerful against walking creatures or teleporting creatures that have nowhere else to stand upon. In the hardmode dungeon, if the player puts their back to the wall, and has only one passage leading into the room they are in, they can lay down a rainbow that eliminates every enemy that comes at them besides the occasional Cursed Skull.
 * For the same reasons, the weapon is exceptionally potent against invasions.

Images
The Rainbow Gun being fired from atop a Dungeon entrance.

A .gif displaying the Rainbow Gun being fired.