Terraria (Wiki): Magic Missile

The Magic Missile is a magic weapon that fires a projectile in exchange for mana rather than ammunition. It is one of the key components in crafting the Sky Fracture.

The Magic Missile fires a controllable exploding projectile if the Player holds the Use/Attack button and moving cursor. Mid-drag, releasing the Use / Attack button will launch the missile in that direction while the cursor will fly straight away from the player if it is still when released. When the missile is launched, it home in on any enemies that are close and attack them (desktop, console, mobile) and can be controlled through gaps of one tile wide and causes an explosion that can damage enemies through a one-block-thick wall. The Magic Missile's mana cost is only for initial casting, and players will regenerate mana while in control, and it will not cost more mana to maintain and direct it.

The Magic Missile has a low use time and a strong knockback which can be used to knock enemies away. It also emits a fair amount of light that is useful for finding caves and can fire through water, unlike Flamelash. Combining the Magic Missile with Binoculars can greatly increase the range over which the missile can be steered.

Combat-wise, the Magic Missile's strong knockback and speed make it effective against multiple enemies.

The Magic Missile is best modified with Mythical for overall stats improvement.