From Scripture, we know that there are three confirmed residents in the Lake of Fire, two humans and one angel. They are the beast (Anti-Christ), the false prophet and the devil (cf. Rev 19:20; 20:10). There are two more confirmed residents; they are Death and Hades (if they are some kind of angelic beings) at the end of this current heaven and earth (cf. Rev 20:14).
Besides these five confirmed residents, the Scripture warns that anyone whose name was not found in the book of life will end up joining the five confirmed residents in the lake of fire (cf. Rev 20:15). There are similar warning from other parts of Scripture.
Jesus warns that a time is coming when the dead will hear his voice and be resurrected. The ones who done good will be resurrected to enjoy life, and the one who have done evil will be resurrected for judgment (cf. Joh 5:28-29). Although the Lake of fire is not mentioned, it is safe to assume that the resurrection for judgment refers to the dead whom Death and Hades gave up to be judged according to what they had done (cf. Rev 20:13). Everyone whose name is not found the in book of life will be thrown into the Lake of Fire (cf. Rev 20:15).
Paul warns that on the day of wrath, God’s righteous judgment will be revealed (cf. Rom 2:5). On that day, God will judge all according to their deeds (Rom 2:6). God will give eternal life “to those who by patience in well-doing seek for glory and honor and immortality” (Rom 2:7 ESV). On the other hand, God’s wrath and fury will be “for those who are self-seeking and do not obey the truth, but obey unrighteousness” (Rom 2:8 ESV). Although the Lake of fire is not mentioned by Paul, it is reasonable to assume that the day of wrath is the same day as when all great and small stand before the great white throne to be judged according to their deeds, that is, what they had done (cf. Rev 20:11-12).
In all these warnings of judgment, it is clear that believers must take this warning seriously. The threat of being thrown into the Lake of Fire is real because the Scripture has already mentioned three, if not five, confirmed residents in it. On the hand, the good news is that no other human being has been named as resident in the Lake of Fire. Thus, no one knows with certainty who else will be in the Lake of Fire.
While no one knows with certainty who will be thrown into the Lake of Fire, the Scripture on the other hand points to a certain path to escape the Lake of Fire. Paul points to Christ as the certain path to escape (saved) from the wrath of God (Rom 5:9; cf. 1Th 1:10). All who believed in Christ are not destined for the wrath of God (1Th 5:9).
Why does God offer a certain path of escape from the Lake of Fire? The answer is God’s love for the whole humanity. The Scripture says, “For God so loved the world” (Joh 3:16a). The “world” refers to the whole humanity. God is motivated by love to save the whole humanity through his only Son, who came not to condemn but to save humanity (Joh 3:17).
While God love the whole humanity, every human needs to make a choice about his Son, Jesus. If they believe, they have eternal life (Joh 3:16b). They are not condemned, that is, they are not destined for the Lake of Fire (Joh 3:18a; cf. 1Th 5:9). On the other hand, if a person does not believe, such a person is already condemned, that is, they are already destined for the Lake of Fire (Joh 3:18b; cf. 1Th 5:9). The reason is that such a person did not believe in the only Son of God, who is the only certain path of escape from the Lake of fire (Rom 5:9; 1Th 1:10).
While Jesus is the certain path of escape from the Lake of fire, all are traveling down the road to the Lake of fire because they have committed sins, not because they did not believe in Jesus Christ. The warning of Scripture is that they will be judged according to what they have done. Is there anyone who does not need salvation? The warning of Scripture is that all have fallen short of the glory of God, and deserve to be thrown into the Lake of fire (cf. Rom 3:22b-23; Eph 2:1-3).
Then, how about those who did not hear about Jesus Christ? From what we know, all will be judged according to their deeds. Does this mean that they do not have an opportunity to escape the Lake of fire? We do not know because Scripture did not clearly say. Since God is loving and Jesus is the only certain path, is it possible that God will send Jesus to them in a different way, eg, dream? Yes, God and Jesus can. Nevertheless, we will never know unless we hear personal testimony of such contact (“conversion of Saul” cf. Acts 9:1-31; Cornelius, Acts 10:1-48).
While we are to be responsible witnesses for Jesus, we must acknowledge that we will never know how God reaches out to those who never hear the gospel from us. We trust in God’s love and goodness to bring Jesus to them. The Scripture does give us a glimpse on how God could have done it (Acts 9:1-31; 10:1-48), but God sees fit not to let us know the details. Just as God is responsible for our salvation, God is responsible for the salvation of those who never hear the gospel from us. The responsibility that does belong to us is to witness for Christ in this world.