Gog and Magog

Allah the Almighty says:
{They said: "0 Dhul-Qarnain! Verily Ya'juj and Ma 'juj (Gog and
Magog) are doing great mischief in the land. Shall we then pay you a
tribute in order that you might erect a barrier between us and them?"
He said: "That (wealth, authority and power) in which my Lord had
established me is better (than your tribute). So help me with strength (of men), I will erect between you and them a barrier. "Give me pieces (blocks) of iron;" then, when he had filled up the gap between the two mountain-cliffs, he said: "Blow;" then when he had made them (red as) fire, he said: "Bring me molten copper to pour over them." So they (Ya 'juj and Ma 'juj (Gog and Magog)] could not scale it or dig through it.
(Dhul-Qarnain) said: "This is a mercy from my Lord, but when the
Promise of my Lord comes, He shall level it down to the ground. And
the Promise of my Lord is ever true"}. (Al-Kahf, 94-98)
And, {Until, when Ya'juj and Ma'juj (Gog and Magog) are let loose
(from their barrier), and they swoop downfrom every mound}. (Al-
Anbiya', 96)