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Play Altered Beast (US_EU_BR edition · English) Online

Altered Beast

Play Altered Beast online on Master System. Gather Spirit Balls and transform to battle Neff’s monsters.

Browser play

Sega Master System — EmulatorJS controls

Default Player 1 keyboard mapping. Change keys in Controller Settings.

Console button	Keyboard
↑ / ↓ / ← / →	↑ / ↓ / ← / →
1 / START	X
2	Z

Open Controller Settings to configure your keyboard or gamepad. Touch controls are available on mobile.

How to Play Altered Beast

Quick start

Press 1 to begin. Use kicks and punches in the graveyard, defeat the two-headed wolves and collect two Spirit Balls to transform.

Controls

Pad left/right: move; down: kneel. 1: kick/start. 2: punch. 1+2 together: jump. Down+1: upward kick while lying back. After transformation, 1 and 2 use the beast’s attacks.

Altered Beast — About this game

Zeus raises a fallen warrior to rescue Athena from Neff. The Master System game begins with close-range punches and kicks, then changes when you defeat two-headed wolves and collect their Spirit Balls. The first ball strengthens the warrior; the second triggers a beast transformation with different attacks. Each round tests that new form against a monstrous guardian.

Altered Beast Game manuals

Cheats

No cheats have been added for this edition.

Player verification and sources

Browser play was reviewed before this edition was published in the catalogue. The date below is the catalogue publication date, not the game’s original release date.

Browser test and catalogue publication date: October 24, 2026
Browsers and devices: PC: Chrome, Edge and Firefox. Mobile: Chrome on Android and Safari on iPhone and iPad.
Player engine and core: EmulatorJS 4.3.0-pre · segaMS
Tested by: rwEmulator

Sources and editorial basis

rwEmulator reviews edition metadata, release information, game manuals and first-hand browser-play notes. Available manuals are linked below; the editorial policy explains how facts are checked and corrections are handled.

Editorial policy and sources Trust center EmulatorJS player help