Meteor Head

Meteor Heads are flying enemies that spawn once you enter a meteorite's crash site. They usually spawn in packs of 3-5 and will override other enemies in the area, meaning that no other enemies will spawn as long as there are Meteor Heads around.

Meteor Heads follow typical Flying AI, with the exception that they do not collide with solid blocks and can fly straight through them.

The suggested way of defeating them is to defend yourself by using your pickaxe. While mining you can hit the Meteor Heads as they're flying towards you, as long they're coming from one direction. Suggested items are a Cobalt Shield to keep you from being knocked around and an Obsidian Skull to prevent damage from the Meteorite itself. A Grappling Hook or Ivy Whip can be used in place of a Cobalt Shield to hold you in place, and Shadow Armor or Feral Claws can increase your pickaxe's swing rate.

Another suggested method is based on the fact that they do not respawn instantly. With a high tier weapon you should be able to kill all of them rather quickly, provided they have grouped up, giving you some time to act without their interference.

Meteor Heads will stop spawning once there are only 49 or fewer blocks of the Meteorite left, which is usually about 10-20% of its total size.