Vanquisher

The Vanquisher is a Mob that drops Nether Stars to any player who dealt at least 1,000,000 damage to it, but the player who spawned it will receive 3 Nether Stars, even if they do not deal the required amount of damage.

Spawning
Vanquishers have a base chance of 1/640 to spawn when any enemy is killed on the Crimson Isle.

Multiple factors can increase the chance of a Vanquisher spawning:
 * After 640, 960, and 1,280 mobs are killed without spawning a vanquisher, the chances are increased.
 * The Kuudra Pet's perk.
 * 's perk increases the chance for a Vanquisher to spawn by 15%.

Combining all of the following: The spawn chance becomes 1/391.68
 * Wither Piper perk