The “lake of fire” is prepared as the last Judgment Sentence for all the wicked in the world (men, angels or otherwise).
But God (Who alone is Good) does not pass a “sadistic or purposeless” sentence in (divine) Fire but actually does put them in a “medicinal fire” (purposed for their betterment) though extremely painful, it serves as the “last” needful remedy to “burn-off” the chaff of “sin, evil or vice” (non-living negative attachments) once and for all out of existence eventually.
Our Blessed Saviour is the only One able to rise with Healing in His Wings to Save them All too at their appointed times into the ages which are coming.
These deep secrets and mysteries are hidden and require a lot of inferences because it’s not so literally spelled out as such in the Bible.
The reason for this is so that “men may not become careless (and sin more meriting greater punishments)” as Sadhu Sundar Singh was told in his spiritual visions regarding heaven and hell.
However, the type of fire in the “lake of fire” need not necessarily be same as its earthly counterpart.
Its characteristics remain unknown to us.
But a “highly possible” explanation to understand both the nature and purpose of this “last Fire” of Judgment may ‘not’ be found directly in the Bible itself but in the non-canonical (once held as Scripture) Book of Enoch instead, as we consider those verses now (with an open mind, not as doctrine but as a “possibility” – I’ve amended the appropriate age or ages literal corrections accordingly to the best of my knowledge):
(1) Lake of fire (“streams of fire” in the “valley of decision”, “rivers of fire”) was originally prepared for the devil and his angels:
“And He will imprison those angels, who have shown unrighteousness, in that burning valley which my grandfather Enoch had formerly shown to me in the west among the mountains of gold and silver and iron and soft metal and tin.
And I saw that valley in which there was a great convulsion and a convulsion of the waters.
And when all this took place, from that fiery molten metal and from the convulsion thereof in that place, there was produced a smell of sulphur, and it was connected with those waters, and that valley of the angels who had led astray (mankind) burned beneath that land.” (Book of Enoch 67:4 – 6)
Compare with the Bible verses:
“Then shall He say also to those on the left hand, Go ye from Me, the cursed, to the fire, the age-during, that hath been prepared for the Devil and his angels;” – Lord Jesus Christ (Matthew 25:41)
“Let the nations be roused; let them advance into the Valley of Jehoshaphat, for there I will sit to judge all the nations on every side.” (Joel 3:12)
“Multitudes, multitudes in the valley of decision! For the day of the Lord is near in the valley of decision.” (Joel 3:14)
“Shall I leave their innocent blood unavenged No, I will not.” The Lord dwells in Zion!” (Joel 3:21)
“As I looked, “thrones were set in place, and the Ancient of Days took His seat. His clothing was as white as snow; the Hair of His Head was white like wool.
His throne was flaming with fire, and its wheels were all ablaze.
A river of fire was flowing, coming out from before Him.
Thousands upon thousands attended Him; ten thousand times ten thousand stood before Him.
The court was seated, and the books were opened.” (Daniel 7:9 – 10)
(2) The “waters of fire” are “for the healing of the body” (purposeful) and also a “punishment for their lustful sins” (a fair recompense) as even this mysterious verse describes:
“But those waters shall in those days serve for the kings and the mighty and the exalted, and those who dwell on the earth, for the healing of the body, but for the punishment of the spirit; now their spirit is full of lust, that they may be punished in their body, for they have denied the Lord of Spirits and see their punishment daily, and yet believe not in His Name.” (Enoch 67:8)
(3) Their punishment remains (lasts to the “age or ages” or “ages of ages”) but a “change toward good for their betterment” will happen (opposite to what they were, evil) in their “spirits”:
“And in proportion as the burning of their bodies becomes severe, a corresponding change shall take place in their spirit to the “ages of ages” (age or ages); for before the Lord of Spirits none shall utter an idle word.” (Enoch 67:9)
This fact that the “spirit” can be “saved” (even of the wicked) is echoed in these Bible verses too (though their “flesh”, where “sin dwells” is destroyed in Judgment). Consider these parallels:
“for for this also to dead men was Good News (or, Gospel) proclaimed, that they may be judged, indeed, according to men in the flesh, and may live according to God in the spirit.” – apostle Peter (1 Peter 4:6)
“to deliver up such a one to Satan (the Adversary) for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.” – apostle Paul in (1 Corinthians 5:5)
(4) The reason ‘why’ these wicked are judged thus is due to “lust” and “denying the Spirit of the Lord”, both of which bars anyone from entering His Kingdom of the Heavens:
“For the judgement shall come upon them, because they believe in the lust of their body and deny the Spirit of the Lord.” (Enoch 67:10)
(5) The waters of punishment change accordingly (in “time”, in “those days”) with respect to the severity and purpose of the punishment deserved:
“And those same waters will undergo a change in those days; for when those angels are punished in these waters, these water-springs shall change their temperature, and when the angels ascend, this water of the springs shall change and become cold.” (Enoch 67:11)
“The servant who knows the Master’s will and does not get ready or does not do what the Master wants will be beaten with many blows.
But the one who does not know and does things deserving punishment will be beaten with few blows.
From everyone who has been given much, much will be demanded; and from the one who has been entrusted with much, much more will be asked.” – Lord Jesus Christ (Luke 12:47 – 48)
(5) Those punished “can’t see” that these are for their betterment and hence “it burns to the age or ages”.
They still need the “Saviour of the World” to be rescued “from their sins” (and even from its consequences in the “lake of fire”, where the water transforms to fire and vice versa):
“And I heard Michael answering and saying: ‘This judgement wherewith the angels are judged is a testimony for the kings and the mighty who possess the earth.’
Because these waters of judgement minister to the healing of the body of the kings and the lust of their body; therefore they will not see and will not believe that those waters will change and become a fire which burns to the age (or ages).” (Enoch 67:12 – 13)
As our Blessed Lord remarks in the analogy below describing that one remains in punishment during the “afterlife judgments” (to the age or ages as its described above —> be it Gehenna, Hell (Hades) or the Lake of Fire) getting out only “after paying the last penny” (for ‘sin’ committed):
“Truly I tell you, you will not get out until you have paid the last penny.” – Lord Jesus Christ (Matthew 5:26)
He cannot Fail.
He Will Reconcile all things, hence Saving the World as it’s written:
“and through Him to reconcile the all things to Himself — having made peace through the blood of His cross — through Him, whether the things upon the earth, whether the things in the heavens.” (Colossians 1:20)
Lastly, remember that He cannot change from His Most Holy Will:
“namely, that God was in Christ reconciling the world to Himself, not counting their (the world’s) trespasses (sins) against them (the sinful world), and He has committed to us the word of reconciliation.” (2 Corinthians 5:19)
This last secret regarding Judgment, do you understand? You decide by your acts after hearing the Truth.
“Many will be purified, made spotless and refined, but the wicked will continue to be wicked. None of the wicked will understand, but those who are wise will understand.” (Daniel 12:10)