According to God's word, they are cast into the Lake of Fire and suffer eternal torment ( Isaiah 66:24, Mark 9:44, Revelation 20:10-15 ).
Finally,
Rev 20:10 And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever.
Rev 20:11 And I saw a great white throne, and him that sat on it, from whose face the earth and the heaven fled away; and there was found no place for them.
Rev 20:12 And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works.
Rev 20:13 And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works.
Rev 20:14 And death and hell were cast into the lake of fire. This is the second death.
Rev 20:15 And whosoever was not found written in the book of life was cast into the lake of fire.
We come to a place which seemingly teaches 'eternal torment' ("...shall be tormented day and night for ever and ever.. ..." ), that is until the context and words are studied.
So, this text does directly speak of "torment". This is never denied, but always accepted. Torment does indeed go with the final 'reward' of the wicked. Jesus, who suffered for all sin, is the example. He suffered (was tormented) unto death. So too the wicked, even as the unrepentant thief next to Him did also experience.
The "day and night" speaks to the time portion/element of the "torment", in that it will be ongoing (without reprieve) until the job is done (ashes), with some being tormented unto death shorter or longer depending on their deeds done (God is Just). This also speaks to the unquenchable part of the "fire" aspect, in that the wicked cannot put out the fire, nor deliver themselves from it. They shall be consumed in it unto "ashes" (see previous texts cited).
The "for ever and ever" part is connected to the "day and night" and "torment" and "fire" in the "lake", in that it means moment to moment (αιωνας των αιωνων; aiwnas twn aiwnwn). In other words there is not a moment that the wicked shall not suffer in the unquenchable fire (lake thereof), until they are carcasses unto ashes. This cannot last eternally, as God is going to create the New Heavens and New Earth where all of that is taking place.
The confusion comes in how the Bible (KJB) uses the words "for ever and ever". The Bible (KJB) does not always use this to mean 'eternal'. It can speak to just a few moments, 3 days, eternal or even distance (when time is not involved).
Can an "αιων" [aiwn, aeon, in either time, distance or space] come to an end? Yes, even as Paul shows in Hebrews:
Hebrew 9:26 KJB - For then must he often have suffered since the foundation of the world: but now once in the end of the world hath he appeared to put away sin by the sacrifice of himself.
Hebrew 9:26 KJB - επει εδει αυτον πολλακις παθειν απο καταβολης κοσμου νυν δε απαξ επι συντελεια των αιωνων εις αθετησιν αμαρτιας δια της θυσιας αυτου πεφανερωται
Notice, "end of the world [aeon]". Notice again:
Titus 2:12 KJB - Teaching us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly, in this present world;
Titus 2:12 KJB - παιδευουσα ημας ινα αρνησαμενοι την ασεβειαν και τας κοσμικας επιθυμιας σωφρονως και δικαιως και ευσεβως ζησωμεν εν τω νυν αιωνι
Notice, "in this present world [aeon]", which indicates that there is an end to the current "world", or existence, and another "world" [aeon], or existence, to follow after it. Thus and "aeon" can come to an end, and is not necessarily eternal. See also "since the world began", "before this world", "this present evil world", "this world", in Matthew 12:32, Matthew 13:22, Matthew 13:39-40 (2), Matthew 13:49, Matthew 24:3, Matthew 28:20, Mark 4:19, Mark 10:30, Luke 1:70, Luke 16:8, Luke 18:30, Luke 20:34-35 (2), John 9:32, Acts 3:21, Acts 15:18, Romans 12:2, 1 Corinthians 1:20, 1 Corinthians 2:6-8 (4), 1 Corinthians 3:18, 1 Corinthians 8:13, 1 Corinthians 10:11, 2 Corinthians 4:4, Galatians 1:4, Ephesians 1:21, Ephesians 3:9, Ephesians 3:21, Ephesians 6:12, 1 Timothy 6:17, 2 Timothy 4:10, Tit 2:12, Hebrews 6:5, Hebrews 9:26; and etc. We now see that "aeon's" can begin, and end, and are not always ongoing without ceasing, and thus context always determines the length, distance, existence, etc.
Notice how the Bible uses the word "for ever":
Jonah 2:6 KJB - I went down to the bottoms of the mountains; the earth with her bars was about me for ever: yet hast thou brought up my life from corruption, O LORD my God.
Jonah 2:6 (2:7) (so-called) LXX - κατέβην εἰς γῆν, ἧς οἱ μοχλοὶ αὐτῆς κάτοχοι αἰώνιοι, καὶ ἀναβήτω φθορὰ ζωῆς μου, κύριε ὁ θεός μου.
In both distance and time, it is impossible for the word "for ever" in Jonah to be eternal, or without end. Not only does earth have limited space [thus
"ends of the earth", dry land is earth, see Genesis 1], but Jonah was only 3 days and 3 nights, timewise, in the belly:
Jonah 1:17 KJB - Now the LORD had prepared a great fish to swallow up Jonah. And Jonah was in the belly of the fish three days and three nights.
Therefore, in either case, "for ever" is limited, in this instance, in distance and time.
In Deuteronomy 23:3 KJB, “forever” means 10 generations. It can also mean “as long as he lives,” or “to death.”; thus see 1 Samuel 1:22, 28; Exodus 21:6; Psalm 48:14 KJB.
Therefore, to attempt to use Revelation 20:10 to teach eternal torment, one must ignore the immediate context of where the sinners are all at, must choose to ignore where God creates the New Heavens and New Earth, must choose to ignore the passages which teach that all sinners become "ashes" after being "tormented" and "burned", must have a skewed idea of the Justness and Justice of God, must choose to think that all sin is equally punished with torment (eternally) rather than torment according to their deeds done, and choose to ignore that the wages for sin is ultimately "death", not being alive, must be ignorant of the sin and sinners represented in the Sanctuary (Psalms 77:13, 73:17) service, and one must be either ignorant or choose to ignore what the Bible teaches about the use of the word "aiwn" in OT and NT usage, and choose to define "for ever" by their own definition, and or confuse eternal life (which the wicked never have) and the "for ever" they live, with the wicked's reward.