Andromeda

Andromeda is a space-themed war-engine capable of destroying planets. It is the final boss in MegaMan Star Force, both the video game and the anime. It's most likely a weapon built by the FM-ians or a legendary creature of Planet FM. Apparently, it needs the Andromeda Key to activate, which Omega-Xis stole from the FM-ians. The FM-ians' main objective throughout the series is to recover the key from him and revive Andromeda. Andromeda is named after the constellation of the mythological princess Andromeda, and maybe also after the Andromeda Galaxy.

MegaMan Star Force
The FM-ians mention it during their raids on Earth, and apparently, Omega-Xis has something they need to activate it - the Andromeda Key. Ophiuca states that it needs two things: the Key and the FM King's control panel. When Omega-Xis leaves Geo, the revived FM-ians ambush him and, despite Harp Note's attempt to help, succeed in taking the Andromeda Key. Apparently, they plan to have Andromeda consume all life and destroy planet Earth, just like it destroyed Planet AM. They start kidnapping people to feed them to Andromeda, but are thwarted by MegaMan and the Satellite Admins.

Later on in the Space Station Peace, after MegaMan deletes all the FM-ian warriors and confronts the FM King, Cepheus, the FM King summons Andromeda. Omega-Xis states that it has an EM body, but all it ever does is eat other EM beings. Half-way through the battle, it transforms into a robotic form. After MegaMan defeats Andromeda, Cepheus sends it for another go at MegaMan, and Geo can't fight anymore because of the King's strong Z-waves. However, it goes cannibalistic and tries to eat Cepheus, but Geo is still helpless. Geo then remembers his friends who are depending on him, and his father, and that gives him strength again. Using one powerfully charged shot, he destroys Andromeda once and for all, saving Cepheus and planet Earth. Geo and Omega-Xis both forgive Cepheus.

Andromeda can be fought in the last wavehole in the Space Station, beyond Ophiuca's door. Once you pulse in, you can't pulse back out until you defeat Andromeda. It can fought repeatedly so long as you still don't have the 6 icons. After defeating it, then defeating the version's Satellite Admin, he tells you to fight the "truly lonely giant". After getting all the icons, going to the place where you find Andromeda will let you battle Andromeda∞ (4000HP). It then stays permanently in that form, and can't be reversed back to its original form. Beating this means you've finished the entire game and its secrets, with an extra screen at the end showing Geo and all his friends and commending the player for his efforts.

MegaMan Star Force (anime)
Andromeda has a similar role in the anime. FM-ians constantly attack Earth in search of the Andromeda Key, which is in the possession of Omega-Xis. When Omega-Xis comes back to help Geo, they battle against the FM-ians but are overpowered, and CygnusWing captures Omega-Xis, obtains the key and prepares to use Andromeda to destroy the Earth. The Satellite Admins Leo Kingdom, Pegasus Magic, and Dragon Sky then stop the fighting and explain to Geo he true nature of Andromeda: a machine designed to destroy planets that once destroyed Planet AM, the home planet of the Admins. They grant him the Star Force to help destroy Andromeda, and they also save Omega-Xis from the FM-ians. While MegaMan battles the FM-ians, the Gemini Spark twins appear and attempt to steal the Key from Cygnus Wing. After MegaMan destroys Cygnus, Omega-Xis destroys the Key. Pat, however, finds its remains. Gemini Spark then gives a fake Andromeda Key to Cancer Bubble, telling him it's the real one, while they keep the real one for themselves.

The FM-ians now have a new goal: to gather enough Negative Energy from humans to revive Andromeda, unaware that Gemini Spark has the real key and is using them to gather Negative Energy so they can use it for themselves. During a mass attack on the city, the fake Key is destroyed, and the FM King Cepheus orders his warriors back to Planet FM, deciding to end the war. GeminiSpark, however, is not content. He murders and erases all his fellow FM-ians since they yield more Negative Energy than humans, revealing that the Key Cancer Bubble had was a fake. Despite failing to delete Harp Note and Cancer Bubble, they proceed to revive Andromeda, which was hidden in an iceberg all along with the Negative Energy they already have, and then use to level several cities across the globe. Andromeda then rises and heads for Echo Ridge, but MegaMan and Harp Note try to intervene. They are, however, quickly overpowered, and are both thrown unconscious into the ocean, only to be saved by Cancer Bubble. Since Harp Note took the full hit for MegaMan, she remains unconscious, while MegaMan confronts Andromeda alone. Even though he uses the Star Force, he couldn’t even damage it, and when he freezes it, it transforms to its robot form and knocks him unconscious on the street, revealing his identity to his friends. The Satellite Admins use the remaining power of the Star Force to destroy Andromeda, sacrificing themselves in the process. MegaMan then finishes Andromeda off. However, it doesn’t end, as Gemini Spark White betrays his other half, Gemini Spark Black, to fully restore the Key and revive Andromeda. Andromeda then digs towards the Earth’s core to blow it up, and Gemini Spark leaves for outer space. MegaMan follows and catches him, but he throws the key towards Earth. MegaMan dives and destroys the key just in time, stopping Andromeda, while Cepheus deletes Gemini and apologizes to Earth and to Omega-Xis.

In a conversation Geo has with Kelvin after he briefly returned from the FM-ians' planet, Kelvin reveals that Andromeda's negative presence around the FM-ians is what caused their evil nature.

Abilities

 * After reaching half HP or so, Andromeda will change to its battle form, which is stationary, and its core cannot be damaged except when it flashes green, or by Breaking attacks.
 * Super Armour : Andromeda cannot flinch.
 * Status Guard : Andromeda is immune to status ailments.
 * Meteor Shower : Andromeda regularly drops a meteor on the player's position. The battle form drops three meteors instead. The meteors cannot be blocked.
 * Giga Missile : Andromeda fires two missiles down two columns at the player. The battle form sends them down all three columns. The missiles can be destroyed or blocked.
 * Big Bang Eater : Andromeda will bite the battlefield with its teeth. This attack cannot be dodged, and is used only by its first form.
 * Big Bang Crusher : Andromeda's battle form slams its fists on the battlefield. This attack cannot be dodged, and is used only by its second form.
 * Nebula Blazer : Andromeda fires a beam down the centre column, or down two adjacent columns. This attack cannot be blocked, and is used only by its second form.

Appearance
Andromeda first appears as a huge monster with a big mouth and large teeth. During battle, it can transform into a robotic, more humanoid form, with its green ball of loneliness being under its chest and a large spike under it instead of legs, its teeth becoming its fingers. Apparently, its hands can start spinning rapidly and act as a drill. Not truly confirmed but its green crystal may be the real Andromeda, the mystical princess of the galaxy.