It is inferred from the Quranic verses, the information provided by Torah and historical evidence that these people lived in north Asia. They were known for their atrocious and barbaric attacks creating catastrophe by ruthlessly killing people in the south and west. However, Dhul-Qarnayn built the wall that kept Gog and Magog from attacking the people whom he met on his journey to east. According to many exegetes of the Holy Quran, these ruthless people will return at the apocalyptic period or the end of time. Some say that their return was the very attack of the Mongols that took place long time ago. Others are of the view that they have not yet returned and that the War of Gog and Magog will happen in the last days after these people come out again.
The main sources from which information is derived about Gog and Magog is the Quran, and there are also some references made about these people in the Old Testament. The exegetes of the Holy Quran and also historians using these sources and studying historical evidence have made some conjectures and guesses about these people.
The story of Dhul-Qarnayn appears in several verses of the Qur'an. It says: “Until when he reached (a place) between the two mountains, he found on that side of them a people who could hardly understand a word. They said: O Zulqarnain! surely Gog and Magog make mischief in the land. Shall we then pay you a tribute on condition that you should raise a barrier between us and them.”
Then the Quran explains how this barrier was built to prevent the invasion of Gog and Magog. It says: “And (Gog and Magog) were not able to surmount, nor could they pierce (it).”
It is understood from these verses that God and Magog were a group of oppressive and cruel people who were prevented from committing further injustice after Dhul-Qarnayn built a barrier between two mountains making them unable to commit further cruelty.
Else where the Quran says: “Even when Gog and Magog are let loose and they shall break forth from every elevated place. And the true promise shall draw nigh, then lo!”
This verse has predicted that the people of Gog and Magog will appear once again in the last days from the mountains. What is understood from the Quran about these people is restricted to these two verses.
However, there are also some references made in the Old Testament. In the Book of Genesis, and the Book of Ezekiel and also in John’s Dream, it is stated that Gog and Magog were a nation or nations settled in the fertile lands of north Asia. They were people who engaged in war, looting and spreading sedition. Apart from the Quranic verses and the text of the Torah which have made mention of this group of people, there are discussions which have been made by historians and exegetes, discussions which refer to historic evidence and allegations which are not reliable and documented.
Late Allamah Tabatabai says in his Tafsir al-Mizan: “The exegetes of the Quran and historians have conducted a lot minute research and investigation into this story and they have delved into this topic with most of them believing that Gog and Magog were a nation residing in the north of Asia.”
They were living across the north from Tibet and China to North Pole and from the west to the land of Turkistan. This has been cited from “Fakihat al-Khulafa” and “Tahzib al-Akhlaq” of Ibn Miskawayh and “Rasail Ikhwan al-Safa”.
Allamah Husseini Tehrani makes an interesting etymological comparison of the word Gog and Magog in different languages. He concludes that “the Chinese origin of these two words are Mongog or Monchuk. Then in the Hebrew language, it was changed into Gog u-Magog (Yaʾjūj wa-Maʾjūj) and in Greek language it turned into Gog and Magog. It can be said that due to similarity between Magog and Mongog, this word has developed from the Chinese word “Mongog” as is the word Mongol or Mughal. Hence, Gog and Magog are the Mongol tribe that have long been living in north east Asia. This big nation sometimes invaded China and at times they attacked Daryal of Caucasia and north of Iran. Sometimes, after construction of a barrier, they attacked north of Europe which is known to them as Scyth. A group of them attacked on Rome as a result of which the Roman state collapsed. The Greeks called them Scythians and the same name has been recorded in Dariush’s Perspolis writings.”
The Quran does not make explicit reference to their destruction and annihilation. In fact, what is understood from the Quran is that they were no longer able to attack, loot and plunder when the barrier was built. As for whether or not they are still alive, there is no verse in the Quran nor any tradition from the Infallibles to describe their present condition. It can be said that according to Ibn Abbass’ recitation of the verse of Sura Anbiya, it is well understood that they are dead because Ibn Abbas has recited the word “hadaba”, which means a high place, as “jadatha” which means grave. In this case, the verse means as such: “When Gog and Magog are let loose and they shall break forth from their graves.” There are also some traditions interpreting this verse saying that in the apocalyptic period or the end times Gog and Magog will reappear in the world. This shows that they are not in the world now and they will return sometime in future.
When it comes to their re-invasion, it is a matter of controversy among scholars with some of them saying that the report of the Holy Quran, which says “they shall break forth” “! surely Gog and Magog make mischief in the land”, is applicable to the Tartar’s (Mughal) invasion during the first half of the seventh century on west Asia. That is because they were the people who at that time rebelled and committed crimes by shedding blood, plundering and destroying cities and towns, killing people and looting their property. The crime they committed has no like in the history of mankind because they invaded China, Turkistan, Iran, Iraq, Syria and Caucasia to Asia Minor. They destroyed the cities or towns that put resistance against them slaughtering their residents in the most brutal way. 
Unlike this group of researchers it can be said that if we assume that Gog and Magog perished very long time ago after the barrier was built and they are expected to return to the world again, we cannot say that they were the Mongols because it is not true to say that they will come out of their graves again.
Conclusively, we must say that whatever has been said regarding them is just probable and we cannot take them as concrete evidence and that we must only suffice to relying on the explicit verses of the Quran only.
 Al-Kahf, 93 – 94.
 Al-Kahf, 97. See
 Al-Anbiya, 96 – 97.
 Husseini Tehrani Sayyid Muhammad Hussein, Me’ad Shenasi, vol.4, p. 85, website for translation and publication of Islamic Sciences series.
 Tabatabai, Sayyid Muhammad Hussein, Al-Mizan fi Tafsir al-Quran, translation, Musavi Hamedani, Sayyid Muhammad Baqir, vol.13, p. 542, Islamic Publications Office, 1374.
 Husseini Tehrani Sayyid Muhammad Hussein, Me’ad Shenasi, vol.4, p. 86.
 Husseini Tehrani Sayyid Muhammad Hussein, Me’ad Shenasi, vol.4, p. 87.
 Vide: Najafi Khomeini, Muhammad Jawad, Tafsir Asaan, vol.12, p. 366, Islamic Publications, 1398 A.H.
 Majlisi, Behar al-Anwar, vol.12, p. 179, Al-Wafa, 1404 A.H.
 Tabatabai, Sayyid Muhammad Hussein, Al-Mizan fi Tafsir al-Quran, translation, Musavi Hamedani, Sayyid Muhammad Baqir, vol.13, p. 542.