The Leviathan is found in Job 41, Psalm 74 and 104, and Isaiah 27. The image is that of a sea monster or sea dragon which is serpent like. Arguably the beast in Revelation 13 that comes out of the sea is also this same Leviathan.
Many have speculated whether this Leviathan was a physical creature. But the Bible clearly does not refer to Leviathan merely as a physical creature but also points to its spiritual meaning. The Bible often gives certain animals spiritual meanings. For example the Holy Spirit is represented by a dove, the Messiah by a lamb, Satan by a snake or a dragon, unclean spirits by birds etc. Leviathan is clearly an evil spirit with snake like qualities which is stealth and cunning.
He is a spirit that cannot be defeated or tamed by man alone(Job 41:9). He is immersed in the midst of mankind, stirring up trouble creating turmoil and chaos (Job 41:31/32). He uses his tongue (Job 41:1) on the pride of men (Job 41:34), leading them into violence (fire) by high sounding thoughts and ideas (Job 41:34).
If we look at the violent history of man, we find it is lofty thoughts and aspirations, sometimes religous, social (communism), racial (Nazism, Rwandan Genocide), together with men’s pride that often cause men to commit atrocities on a grand scale. So we find that all through human history, Leviathan have been active.
But there is a day when the Lord will punish this Leviathan (Isa 27:1). In that day the Lord will use His sword (His word), to slay this monster (Isa 27:1). He will use His people to fill the world with good fruit.
Hab 2:14 For the earth will be filled with the knowledge of the glory of the Lord, as the waters cover the sea.
Perhaps we are not living in that day, the day the Lord will finally destroy Leviathan. But the spirit of Leviathan like the spirit of antichrist is already active and we are to battle these spirits in our own lifetimes as the Lord leads. I think the spirit of Leviathan is most manifested in anti-semitic, anti-Israel and anti Christian sentiments. This is true in the times of the Roman Empire, then in Nazi Germany, through the Communist movement, and now in the radical Islamic resurgence. We also find that as the western nations loses their belief in Christ, they will also become more anti-semitic and anti-Christian and will be easily swayed by the works of Leviathan.
We already see in Europe and in the United Nations the spirit of Leviathan working. We cannot battle this just by human methods like education, discussion or debate. This is spiritual warfare and we must fight with spiritual weapons and spiritual armour. We need to know how to use God’s word and how to pray and also, casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ (2 Cor 10:5).