The Emperor Ing is the leader of the Ing Horde, and the main antagonist of Metroid Prime 2: Echoes. It is the oldest and strongest of its species.
When a Leviathan from the planet Phaaze impacted Aether, the devastation of the impact created a trans-dimensional duplicate of Aether called Dark Aether, due to the planet's unstable nature, and the Ing Horde was born. The Emperor Ing was the first of its species to be born, and has since resided in the Sky Temple, where it commands its forces and gained strength from the Light of Aether that was divided between the Great Temple (on Aether) and the Sky Temple when Dark Aether was born, and great amounts of Phazon energy. The Luminoth (of Aether) and the Ing fight a long war over the planetary energy, with the Ing having the advantage.
However, Samus Aran comes to Aether to look for a missing Galactic Federation squad, and gets involved in the war, traveling between Aether and Dark Aether to recover the stolen planetary energy using an Energy Transfer Module that the Ing took from the Luminoth, but she recovered from them. In the end, Samus infiltrates the Sky Temple, where she observes the Emperor Ing taking the remaining Light of Aether into another room through the ceiling. Samus follows the Emperor Ing into its Sanctum. After a fierce battle, Samus defeats the demonic monstrosity and reclaims the Light of Aether, destroying Dark Aether, and the Ing, for good.
In the first part of the battle, the Emperor Ing attempts to attack Samus with its four tentacles, and also by firing lasers from its eye, which it exposes after the tentacles are destroyed. The eye has two protective hemispheres that rotate around it. To damage the eye, Samus has to aim for the gap between the hemispheres. Eventually, the Emperor Ing regenerates its head with more tentacles. Thus, Samus must repeat her plan of attack.
After taking heavy damage, the Emperor Ing encases itself in an impenetrable shell to recuperate. Samus must use the magnetically-charged nature of the shell to her advantage, and Spider-Ball along the shell, attacking the 11 vents, which spew poisonous gas and produce tentacles. The only way to damage the vents is by destroying the tentacles that emerge. After destroying all 11 vents, the shell explodes, revealing the Emperor Ing's final form.
In the final round of the battle, the Light of Aether and the Phazon energy have enhanced the Emperor Ing's power considerably, and also exposed the beast's now unstable heart and given the creature more mobility. To defeat the Emperor Ing this time, Samus must aim for its heart, protected by a mouth-like opening with strands of flesh, and also turn the heart's color to light or dark, and then attack it with the opposite polarity beam; Light Beam for dark, Dark Beam for light; she can't damage the creature while it's heart is orange. Luckily, the Annihilator Beam is effective on all three colors. The Emperor Ing's attacks this time include multiple trans-dimensional beams, jumping, stomping, charging, shockwaves (usually when it stomps or jumps), a beam of dark (that can freeze Samus) or light energy (that can set Samus on fire), and unleashing Nightbarbs or small white creatures that protect it from harm.
The energy beam attacks and the protective swarms of Nightbarbs and small white creatures can only be used when the Emperor Ing's heart is light or dark, though its charging, jumping, stomping, shockwave, and trans-dimensional beam attacks can be used any time. As the Emperor Ing takes more damage, its heart glows brighter. When the final blow is dealt, the Emperor Ing stumbles backwards and collapses to the floor before exploding into purple particles, leaving behind the last of the Light of Aether.