Cyber King doesn't spawn on its own. The only way to summon it is upon the death of the Mothership.
The Cyber King is a flying robot that spawns Cybermites. Once the Cyber King is at half health, he will begin to shoot more projectiles that move much faster and are harder to dodge. He will continue to receive projectile speed and fire rate buffs the more he is damaged until he is defeated.
The Cyber King has 3 distinct attacks.
He always starts off by shooting red laser discs at the player. These discs clip through walls and deal 70-96 damage if hit.
His other attack is he hovers into the air and shoots lots of slow red lasers towards the Player. These also deal 70-96 damage.
His final attack is he starts spinning and shoots purple lasers in random directions. these projectiles deal 56-76 damage.
In Expert Mode Cyber King has no new movesets.
However his Cybermites gain 150 hp and deal 20 more damage.
All of the Cyberking's projectiles now deal double damage.