Terraria (Wiki): Meteor Staff

The Meteor Staff is a Hardmode magic weapon that fires a falling projectile from the sky in exchange for mana rather than ammunition.

The Meteor Staff's projectiles land in the direction of the cursor rather than the intended enemy and cannot go over solid objects, but may traverse through walls and platforms and spawn about 40-42 tiles above the player, it might even immediately crash with any block in their way. Due to their mana costs and attacks, the Meteor Staff is one of the least mana-efficient weapons, much like the Luna Flare. It could be considered the Daedalus Stormbow's magic counterpart.

When used, the Meteor Staff has a low use time and a strong knockback which can be used to knock and pierce enemies away. It emits a high amount of light particles that are useful for illuminating the minimap. Lock On mechanic doesn't work with the Meteor Staff however when the staff comes in contact with an enemy, it explodes and allows the player to attack several targets at once,

Combat-wise, the Meteor Staff's strong knockback and speed make it effective against multiple enemies and is useful in early Hardmode. It is effective against the Flying Dutchman as it can't go over the walls and the Martian Saucer which can't go through ceilings but can pass through blocks (desktop, console, mobile).

The Meteor Staff is best modified with Mythical for overall stats improvement.