Mir (boss)
The final phase of the final boss battle of Ar tonelico: Melody of Elemia, this is Mir's true form, shielded by a barrier of pure hatred. Although her HP is lower than any of her previous virus forms, she is still a pretty dangerous foe, as it can be seen from her stats and skills: Ruined World, which deals large physical damage to a single target; and Falling Sky, which has the distinction of being the only attack in the game capable of hitting all party members in the field, including Reyvateils. Aside of that, it hits for extremely large physical and elemental damage, so if your party has low defense, it most likely kill them all in a single hit. Like with Shadow Mir, the strategies for this battle change depending on if you're fighting against her for the Bad Ending or any of the True Endings.
Bad Ending
Your party will be weaker and most likely, severely worn out after the battle with Shadow Mir, so you'll have to take additional precautions. Make sure to debuff her with some items like the Quicklezz RX or the Neo Hitlezz to reduce the risk of her attacks wiping out your party, and concentrate your Vanguards on attacking her while leaving your Reyvateil on healing/buffing duty. Given that Falling Sky could instantly wipe out your Reyvateil, this would waste all of the Harmonics and Burst you had built up, so unless you're feeling especially brave or lucky, don't attempt to use Red Magic against her.
True Ending
At this point you should have stats enough for at least your Vanguards to survive Falling Sky without much problem, while you can also use some Grathnodes like Almighty Power, Aegis Protector or Don Leon's Power to power-up your Reyvateils so they can also withstand said attack. If your Reyvateil happens to be capable of surviving these attacks, then don't play around: charge the best Song Magic she has at the moment (Ar tonelico, Tower Connection or Child of Light), and then let it loose as soon as it has reached Burst Lv. 4 to instantly end the battle. Otherwise, you will have to apply the same strategies used for the Bad Ending.
Other Apperances
A depiction of Mir in this same form appears in Jakuri's Lv.7-C Cosmosphere as a demonstration of her hatred towards humans for what they did to her EXEC_HARMONIOUS/. song, while also being the character for her Heart's Prison Song Magic, which increases the defenses of the party while it's being sung.