Polycephalus

Polycephalus is a boss that can appear:

In the Catacombs and the Flooded Caves.
Only in the Catacombs.

Behavior

Polycephalus burrows underground when Isaac is not within range. While burrowed he becomes invincible and follows Isaac's movements. When close to Isaac, he pops out and performs one of the following attacks:

Sprays out a cluster of projectiles towards Isaac, similar to Monstro, but more drawn out.
Fires a spread of 3 projectiles at Isaac.
Shoots out 8 projectiles in all directions.
Summons a Round Worm.

He will stay vulnerable for a few moments after performing an attack before quickly burrowing underground again.

Champion Versions

Red: Summons

Para-Bites instead of Round Worms. All projectile attacks are replaced with a ring of six projectiles.

Pink: Two Polycephaluses, each with 50% HP (100), replace the normal Polycephalus. They do not spawn Round Worms.

Gallery

Red Champion Polycephalus.
Pink Champion Polycephalus.
Polycephalus as one of Delirium's forms.

Trivia

The Stain is his posthumous version, who also shows up in Chapter 2. Polycephalus is one of four bosses to have their posthumous version in the same chapter, the others being Gemini having Blighted Ovum in Chapter 1, Chub having Carrion Queen in Chapter 2 and the Tuff Twins having The Shell in Chapter 2.5.
- However, Polycephalus is the only one of them to have their posthumous version in the same environments as well, sharing both the Catacombs and the Flooded Caves with The Stain. The only difference is that The Stain can appear in Caves as well, where Polycephalus cannot.
  - This is no longer the case as of Repentance, since Polycephalus no longer appears in the Flooded Caves while The Stain no longer appears in The Catacombs.
Polycephaly is the condition of having more than one head.
Polycephalus shares his name with a cactus.
Polycephalus is one of the four bosses that can be spawned by It Lives!, the other three being Chub, Fistula and Teratoma.
Prior to Booster Pack #5, Red Champion Polycephalus could spawn Scarred Para-Bites if he was fought in the Scarred Womb.