It will also attack the Ender Dragon in the Overworld and the Nether. If it is spawned in the End, it will prefer to attack any nearby Endermen, but it will also attempt to pursue and attack the Ender Dragon if there are no other nearby targets, but only extremely rarely that it will actually shoot the Ender Dragon. If shot by another Wither, it will shoot each other and rise indefinitely. If no mobs are around, the Wither will teleport behind the player. If a wither shoots a skull at a non-undead mob, but the skull hits an undead mob, the undead mob will become hostile to the Wither, but cannot deal damage. Each of the 3 heads fires heads, allowing a Wither to attack up to three different entities at the same time.

Upon noticing non-undead mobs, the Wither will attack them with a projectile called the “Wither skull”. The Wither is an extremely aggressive demon that is hostile to a player and all mobs except other Withers and 'undead' mobs. If the Wither's health goes below 151 ( x 75.5) or 301 ( x 150.5), The wither will turn blue and will become invulnerable to arrows. When it is at full health it will explode, and send a noise heard all across the world. The wither will spin white while loading health, at this mode it is invulnerable, but will not move or attack, only slowly fall down. Also, the sky will turn darker when you are within a certain range.

The Wither looks like a 'demon' creature, and it is a black, skeletal beast with 3 Wither skulls as heads along with a body that consists of a skeletal spike and three prehensile ribcages.

How to make a mob invulnerable