One of the signs of the reappearance of Imam Mahdi (as), is the coming of a creature gone astray that misleads others by the name of “Dajjal”. In Arabic, any liar can be called dajjal. There are many unusual descriptions about him, but since these descriptions are mostly found in the sources of our Sunni brothers and the hadiths containing these descriptions aren’t ones that can be depended on because of their weak chains of narrators, these hadiths are unreliable.
His role in misleading others is so important that it warns us to be aware of all things that might contribute to our misguidance.
Is he human? Is he technology? Is he the devil himself? Or is he/it something else other than these? There are different viewpoints on the answer to this question. Our advice is for all to refrain from anything that might lead to one’s misguidance and for no one to be of his adherents so that we never become one of his helpers and followers and of those deceived by him!
One of the signs of the reappearance of Imam Mahdi (as) is the coming of the “Dajjal”. According to Arabic literature experts, any liar and trickster can be called a dajjal.
Different unusual traits have been related to him in hadiths (in which are mostly found in Sunni sources), namely: he falsely claims his lordship, is high in age, along with him is fire and water, he cures the blind and those suffering from leprosy.
The commander of the faithful, Imam Ali (as) was busy delivering a sermon when he repeated three times: “Ask me (all that you need) before you lose me.” A righteous individual by the name of Sa’sa’ah ibn Sawhan stood up and asked: “Oh commander of the faithful! Who is the Dajjal?”
In response to this question, Imam Ali (as) replied: “Be aware that the (name) of the dajjal is Sa’ed ibnul-Sa’ed. The unfortunate one is he who acknowledges and accepts him, and the fortunate being the one who rejects him. He will emerge from a place called “Isbahan”, from an area which is known to be the area of the Jews. His right eye is shut, bearing no eyeball.
His other eye is in his forehead, shining so brightly that it resembles the morning star in brightness. In his eye there is a piece of meat that seems to have mixed with some blood and on his forehead, in between the two eyes, it has been written “Kafir” in a way that every literate and illiterate person can read. He travels over the oceans and the sun accompanies him. In front of him, there is a mountain of smoke and behind him there is a white one that people perceive to be food. He will appear during a very hard drought. He will be riding a dark or green donkey. Every step this donkey takes is equal to one mil (mile). He will travel and go here and there on earth. Every water source or spring that he crosses will turn and remain dry till the Day of Judgment. He will shout with a voice heard by all in the East and the West saying: “Come to me, Oh friends and followers of mine!” I (am a God) who has created, who has created the faces, has measured every persons portion (of sustenance), and is your guide. I am the exalted Lord!” He is a liar! He is Allah’s (swt) enemy...and in the end he will eventually be killed by the one Isa (pbuh) prays behind (Imam Mahdi (as))”.
As for who the dajjal really is, one can't reach a definite conclusion, but in a nutshell, it can be said there are several possibilities regarding this matter:
1) The dajjal is a true person that does extraordinary things using witchcraft and magic that will appear at the end of time. He will be the head of a great trouble-making that will take place for all of mankind. As the literal meaning of dajjal suggests, he is a user of witchcraft and a trouble-making individual with many materialistic facilities and capabilities. Some hadiths name him “the messiah of misguidance” which is the opposite of “the messiah of guidance”, meaning Prophet Isa (pbuh).
During the reappearance of Imam Mahdi (as), he will begin to work against him. He is of those who have long lives and is and will remain alive until the day he appears. He will take over the whole world expect for Makkah and Madinah.
2) Iblis or Satan is the dajjal.
3) The Sufyani is the dajjal.
4) The dajjal has a symbolic and secret side to it (and isn't a true person):
“The dajjal symbolizes the highest levels of civilization, culture and Western technology that are in conflict with Islam and its principles; a culture that tries to conquer and enslave all. We can clearly see today how the West’s materialist culture and technology has taken over all societies today, even Muslim ones…”
For further reading:
Dajjal, Dorughguye Faribandeh, Maw’ud Magazine, no.4.
 Of course this sign has been counted as one of the signs of the Day of Judgement (Sunan Tirmidi, vol.4, pp.507-519; Sunan Abi-Dawud, vol.4, pg.115; Sahih Muslim, vol.18, pp.46 and 81), yet in Shia hadith sources it has been counted as one of the signs of the nearness of the Day of Judgment (Biharul-Anwar, vol.6, pg.296, chapter 1 (The signs of the hour (Day of Judgment) and the story of Ya’juj) and also the signs of the reappearance of Imam Mahdi (as). There is no problem in this sign being both the sign of the Day of Judgment and the reappearance of Imam Mahdi (as), because his reappearance is one of the signs of the end of time and the Day of Judgment.
 Sunan Ibn Majah, vol.2, pg. 1360.
 Sahih Muslim, vol.8, pg. 205.
 Sahih Bukhari, vol.8, pg. 103.
 Musnad Ahmad, vol.5, pg. 13.
 Lotfollah Safi, Muntakhabul-Athar, Chapter 3, pg. 532, hadith 8.
In some hadiths it has been stated that he will eventually be killed by Prophet Isa (pbuh) (Biharul-Anwar, vol.14, pg.348, chapter 24) or it has been stated that he will be killed by Prophet Isa (pbuh) at a gate in Sham. For further information, see: Biharul-Anwar, vol.52, pp. 193 and 209; Kamaluddin, 525 and 526; Kashful-Ghummah, vol.3, pg.281; Al-Masa’ilul-Ashr, printed in the works of Sheikh Tusi, vol.3, pg. 122; Irshad, vol.2, pg. 371; Kanzul-Ummal, vol.14, pp. 198-200.
Of course, there is no conflict between these two statements that Prophet Isa (pbuh) is one of those who takes orders from Imam Mahdi (as) and one can relate the doing of a soldier to his commander.
 Al-Faqih, vol.2, pg. 564, the chapter on the respect and virtue of Medinah; Tahdhib, vol.6, pg. 12, chapter 5, The respect and virtue of Medinah.
 Seyyid Muhammad Sadiq, Tarikh ma badal-Dhuhur, pp. 141 and 142. Quoted and obtained from: Ali Asghar Rizvani, Maw’ud Shenasi, pg. 533.