Part 7

Learn how to defeat Blastocyst, Chub, and The Duke of Flies in The Binding of Isaac: Rebirth. This guide covers their attacks, phases, and strategies for survival.

This section covers boss battles in The Binding of Isaac: Rebirth, specifically Blastocyst, Chub, and The Duke of Flies.

Blastocyst

Blastocyst is a boss found in The Womb 1. It is known for being a time-consuming and frantic battle.

Attacks:

• Small hop: A simple hop that is easy to dodge.
• Slightly larger hop: Upon landing, Blastocyst sprays blood in a random direction.
• Large hop: Upon landing, Blastocyst shoots eight small blood drops in all directions.

Phases:

1. Stage 1: One large Blastocyst. Stay far away and keep firing. Dodge random blood sprays.
2. Stage 2: Splits into two smaller Blastocysts. They have different attacks:
   • Small hop: Similar to the first stage, but be aware of two enemies.
   • Medium hop: Upon landing, they shoot four large blood drops diagonally or N, S, E, W.
   Keep attentive and ready to dodge both attack patterns.
3. Stage 3: Splits into four even smaller Blastocysts. They move more and have the following attacks:
   • Small hop: Similar to previous stages.
   • Blood shot: Each Blastocyst shakes before shooting four large drops N, S, E, W.
   Dodging becomes more hectic. The shake is a forewarning for the blood shot.
4. Final Stage: Gelatinous shields break, leaving Blastocysts that only cause touch damage. Focus on killing one at a time.

Keep patient and don't drop your guard.

Chub

Chub is a boss found in the Caves. It is described as a 'Charger on steroids' but is relatively easy.

Attacks:

• Spawn Charger: Spawns a Charger enemy.
• Charge: Charges at the player. This attack deals a full heart of damage.

The battle starts with Chub and 3 Chargers already spawned. The best strategy is to focus damage on Chub. Dodge Chargers unless they pose an immediate threat. If Chub charges, dodge it like a normal Charger, being mindful of walls. Bombs can be used by placing them in Chub's path during a charge to stun him and deal significant damage.

The Duke of Flies

The Duke of Flies is a boss found in the Basement. He floats around and coughs up flies.

Attacks:

• Spawns 3 red-bodied flies.
• Spawns 1 large red-bodied fly.
• Push move: Stops circling flies and causes them to attack the player.

Large red-bodied flies attack immediately upon spawning and deal one full heart of damage. The Duke's moves depend on the number of flies circling him:

• If 6 small flies circle Duke, he uses the push move.
• If 5 small flies circle Duke, he uses the push move or spawns 1 large fly.
• If 4 small flies circle Duke, he spawns 3 small flies.