The Gravemind is the most advanced version of Halo’s Flood species (you can find pictures of him on Halopedia). He controls all flood warriors, everywhere, at once. Along with this, his ability to absorb the memories of fallen foes and possess the knowledge of all previous Graveminds makes him nearly omniscient. He is your enemy in-game, with Master Chief finally destroying him in Halo 3.
Let’s examine the Gravemind (and by extension the Flood) according to the Bible:
*Note: Gravemind quotes are in italics, and scripture quotes are in bold italics.
Lines from Halo 2:
“There is much talk, and I have listened, through rock and metal and time. Now I shall talk, and you shall listen.”
“Silence fills the empty grave, now that I have gone. But my mind is not at rest, for questions linger on. I will ask, and you will answer.”
“[God speaking to Job] Gird up now thy loins like a man; for I will demand of thee, and answer thou me.” (Job 38:3)
Lines from Halo 3:
“Do not be afraid. I am peace; I am salvation.”
“[A prophecy concerning Jesus] For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.” (Isaiah 9:6)
“For God hath not appointed us to wrath, but to obtain salvation by our Lord Jesus Christ,” (1 Thessalonians 5:9)
“For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.” (Romans 1:16)
“Therefore I endure all things for the elect’s sakes, that they may also obtain the salvation which is in Christ Jesus with eternal glory.” (2 Timothy 2:10)
“Child of my enemy, why have you come? I offer no forgiveness, a father’s sins, passed to his son.”
“And the Lord passed by before him, and proclaimed, The Lord, The Lord God, merciful and gracious, longsuffering, and abundant in goodness and truth, Keeping mercy for thousands, forgiving iniquity and transgression and sin, and that will by no means clear the guilty; visiting the iniquity of the fathers upon the children, and upon the children’s children, unto the third and to the fourth generation.” (Exodus 34:6-7)
“I have beaten fleets of thousands! Consumed a galaxy of flesh and mind and bone!”
“I will utterly consume all things from off the land, saith the Lord.
I will consume man and beast; I will consume the fowls of the heaven, and the fishes of the sea, and the stumbling blocks with the wicked: and I will cut off man from off the land, saith the Lord.” (Zephaniah 1:2-3)
“I will rise again.”
“And he [Jesus] began to teach them, that the Son of man [Jesus] must suffer many things, and be rejected of the elders, and of the chief priests, and scribes, and be killed, and after three days rise again.” (Mark 8:31)
From every quote listed, we can see that the Gravemind represents God. This is called “another Jesus” in 2 Corinthians 11:4.
In one of several backwards messages found in music in the series (just look at the Halo Nation Wiki article about this subject), the Gravemind speaks in the music track Destroyer’s Invocation found in Halo 2:
“…I have walked among men and angels for three thousand years. Time has no end… no beginning… no purpose.
I wander the earth, seeking forgiveness for my horrible crimes against God and man.
I live to see death and destruction, evil… over the light, but the light cannot be extinguished.
I live in a prison of my own demise.
I am lost…in time”
Let’s break that down to show the Biblical contradictions, and who the Gravemind is representing in this case:
“…I have walked among men and angels for three thousand years.”
“And the Lord said unto Satan, Whence comest thou? Then Satan answered the Lord, and said, From going to and fro in the earth, and from walking up and down in it.” (Job 1:7)
“Time has no end..”
“But the end of all things is at hand: be ye therefore sober, and watch unto prayer.” (1 Peter 4:7)
“But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.” (2 Peter 3:10)
“no beginning…”
“In the beginning God created the heaven and the earth.” (Genesis 1:1)
“I wander the earth,”
“Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour:” (1 Peter 5:8)
“seeking forgiveness for my horrible crimes against God and man.”
“Therefore rejoice, ye heavens, and ye that dwell in them. Woe to the inhabiters of the earth and of the sea! for the devil is come down unto you, having great wrath, because he knoweth that he hath but a short time.” (Revelation 12:12)
“over the light, but the light cannot be extinguished.”
“Thy word is a lamp unto my feet, and a light unto my path.” (Psalm 119:105)
“ For all flesh is as grass, and all the glory of man as the flower of grass. The grass withereth, and the flower thereof falleth away: But the word of the Lord endureth for ever. And this is the word which by the gospel is preached unto you.” (1 Peter 1:24-25)
“I live in a prison of my own demise.”
“And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand. And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,” (Revelation 20:1-2)
From the statements in Destroyers Invocation, we can reasonably assume that the Gravemind also represents Satan. Doubly so, since quite a few things he says (such as “Time has no end… no beginning…“) go against the Bible. This is much like how Satan spoke lies to Eve in Genesis 3.
The mixing of the good with evil-God and Satan, is both unscriptural and wrong:
“But ye [Christians] are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvellous light;” (1 Peter 2:9)
“Her priests have violated my law, and have profaned mine holy things: they have put no difference between the holy and profane, neither have they shewed difference between the unclean and the clean, and have hid their eyes from my sabbaths, and I am profaned among them.” (Ezekiel 22:26)
“Woe unto them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter!” (Isaiah 5:20)
Video Games and the Bible 
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When you look deeper into the Halo lore, it reveals that an advanced, transentient race known as the Precursors created life and gave them sentience. One of their creations, the Forerunners, rebelled against them in jealously of the Humans, and slaughtered the Precursors to near extinction. The handful of remaining Precursors used their knowledge of Neurophysics to turn themselves to biological dust in the hopes of rebuilding after the threat was gone.
THIS is where the Flood come in. The biological dust, over thousands of years rotted away and corrupted. When Humans first came into contact with it, they began mutating and twisting into what is now called the Flood. Time, rebellion and corruption basically twisted what is essentially God, into a much darker version of himself. That is Gravemind. That is why there is a contradiction in his words. Gravemind was not kidding when he called himself “A monument to all of your Sins”.
The quote “Child of my enemy, why have you come? I offer no forgiveness, a father’s sins, passed to his son.” is actually a reference to how the Humans are the heirs to the Forerunners (that is why the Forerunners where jealous) and a reference to how the Forerunners “Sinned” by slaughtering their creators.