[FairyKing]

I have a rough idea of Kamen Rider Mars's forms, based on various space phenomena:

Forms unique to Kamen Rider Mars Deimos:
- Lightspeed Mode, base form with blinding speed
- Binary Star Mode, super form with higher overall stats, can only be activated by both brothers together
- Timewarp Mode, mobility form with teleportation powers, but prolonged use damages the user's body
- Supernova Mode, ultimate form with high speed and explosive powers

Forms unique to Kamen Rider Mars Phobos:
- Gravity Mode, base form with crushing strength
- Binary Star Mode, super form with higher overall stats, can only be activated by both brothers together
- Alien Mode, berserker form with razor claws and regeneration, but it makes the user act like a feral beast
- Black Hole Mode, ultimate form with high strength and gravity control

Forms unique to Kamen Rider Eris:
- Vacuum Mode, base form that can absorb energy
- Dark Matter Mode, ultimate form that can absorb energy and use it to form constructs (weapons, shields, blasts, etc.)

Forms traded between the riders:
- Comet Mode, melee form with icy punches
- Eclipse Mode, stealth form that can turn invisible
- Asteroid Mode, defense form with rocky armor
- Solar Flare Mode, gunner form with flaming bullets
- Magnetic Mode, hacking form that can interfere with technology
- Nebula Mode, evasion form that can turn into gas (yes, like Sabela)