The word dajjal is derived from the word dajl which means falsification. In Arabic, the word dajala means 'to mix', this word is used for the things or events where the deliberate falsification is done. And therefore the word dajjal is given to that one eyed creature because of his lies, falsification and kufr.
The most important thing about the ummah of Prophet Muhammad s.a.w.w is that we are told about dajjal, while no other prophets told Their people about him. We are told about him because there will not come any prophet after Muhammad s.a.w.w till the last day. there are some ahadith indicating how will dajjal look and what will he do and why is he the biggest fitnah. Below are given those ahadith.
It is narrated on the authority of 'Abdullah b. Umar that the Messenger of Allah (may peace be upon him) said: I found myself one night near the Ka'bah, and I saw a man with wheat complexion amongst the fair-complexioned men that you ever saw. He had a lock of hair the most beautiful of the locks that you ever saw. He had combed it. Water was trickling out of them. He was leaning on two men, or on the shoulders of two men, and he was circumscribing the Ka'bah. I asked, What is he? It was said: He is al-Masih son of Mary. Then I saw another person, stout and having too much curly hair, and blind in his right eye as if it was a full swollen grape. I asked Who is he? It was said: He is al-Masih al-dajjal.
(Sahih Muslim, Book #001, Hadith #0323)
Narrated Jabir ibn Abdullah: Muhammad ibn al-Munkadir told that he saw Jabir ibn Abdullah swearing by Allah that Ibn as-Sa'id was the dajjal (Antichrist). I expressed my surprise by saying: You swear by Allah! He said: I heard Umar swearing to that in the presence of the Apostle of Allah (peace be upon him), but the Apostle of Allah (peace be upon him) did not make any objection to it. (Sunan Abu Dawud, Book #37, Hadith #4317)
Narrated Fatimah, daughter of Qays: The Apostle of Allah (peace be upon him) once delayed the congregational night prayer. He came out and said: The talk of tamim ad-Dari detained me. He transmitted it to me from a man who was on of of the islands of the sea. All of a sudden he found a woman who was trailing her hair. He asked: Who are you? She said: I am the Jassasah. Go to that castle. So I came to it and found a man who was trailing his hair, chained in iron collars, and leaping between Heaven and Earth. I asked: Who are you? He replied: I am the Dajjal (Antichrist). Has the Prophet of the unlettered people come forth now? I replied: Yes. He said: Have they obeyed him or disobeyed him? I said: No, they have obeyed him. He said: That is better for them. (Sunan Abu Dawud, Book #37, Hadith #4311)
And there is a ling hadith (Sahih Muslim, Book #041, Hadith #7015), which describes the dajjal, his appearance and how will he be killed. This liar will be killed by the hands of ESA a.s. this falsifier will be so confident and people will obey him so much that they will even believe him as god when he will say that he is god. Those who will reject him will suffer but for them is the true reward of ALLAH swt waiting because they will be the people who will not fell prey to that liar.
All we need is to fear that time of tribulation and test in which many people will not pass. The present system is preparing for the arrival of dajjal. We live in the world run by interest money. Rich are getting richer and they are preparing to welcome their master, the dajjal.
