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Monstro in-game boss portrait

Repentance · Regular boss · Boss #1

Monstro

A random boss-pool encounter found in Basement, Burning Basement.

Read fight guide
ChapterChapter 1
Base HP250
Floor pools2
Locations2

Encounter map

Where to find Monstro

Random boss pools
BasementBurning Basement

Monstro appears in 2 random floor pools. The weights below are relative to the other entries in each pool, not a guaranteed encounter chance.

Compare bosses in basement

Fight guide · Basement / Burning Basement

How to fight Monstro

Monstro teaches two early habits: leave space for a projectile spread and move when a boss jumps toward you.

Normal boss behavior in Repentance. Champion variants can change these patterns.

Before entering

Choose an open area where you can step sideways. Keep firing from a distance instead of following every hop.

  1. 1

    Short hops

    Watch for: Monstro hops toward Isaac and can close the gap while you aim.

    Try: Back away as he approaches, then resume shooting from outside his landing area.

  2. 2

    Spit volley

    Watch for: He coughs a scattered cluster of projectiles toward you.

    Try: Use the space between shots and make a controlled sidestep instead of running through the whole cluster.

  3. 3

    High jump

    Watch for: Monstro leaves the screen, tries to land on Isaac, and releases another projectile burst.

    Try: Move away from your previous position and keep watching for the shots after he lands.

Reviewed encounter notes. Actual openings vary with your build. Full behavior reference ↗
All boss fight guides

Game-file pools

Spawn entries

2 entries
basementWeight1Double TroubleNot listed
burning basementWeight1Double TroubleNot listed
Game-file referenceRaw data and official artEntity fields, portrait files, and source notes for this boss.

Raw entity values

Health and entity data

Base HP
250
Stage HP scaling value
0
Entity ID and variant
20.0
Contact damage field
1

These are raw entity fields. Armor, floor scaling, phase transitions, shared health, and scripted waves can make the fight differ from the base HP value.

Asset mapping

Official portrait assets

The Monstro versus-screen portrait comes from the supplied game art. The original filenames are retained below.

Monstro official game portrait
Monstro official boss-name graphic
Portrait file
Portrait_20.0_Monstro.png
Boss-name image file
BossName_20.0_Monstro.png

Source notes

How this record is built

Boss identity and portrait metadata come from bossportraits.xml. Random floor membership, weights, and Double Trouble room IDs come from bosspools.xml. Health and entity fields come from entities2.xml. Fixed story locations and route explanations are reviewed editorial context.