Dajjal is one-eyed, and today's humanity, blinded by its system, too. It is spiritually blind. Only a fraction of people still rely on its intuitions and instincts, on the voice of the heart, in a world where rationality is required in all everyday activities.
The Messiah will guide the Muslims and humanity back to God's guidance and the true understanding of religion. His special status is that he himself is not created by the unification of opposing poles, but comes directly from God. He comes directly from unity. He is called the ruhun mina Llah (Spirit from God) and kalimatu Llah (the Word of God).
Jesus and his mother Mary are the only people, according to prophetic tradition, who were not touched by Satan at the time of birth. They are completely free of sin. As the messenger of God, he brought religion back to its original form and freed it from the corruption that had befallen it. At the end of time, he will establish Islam worldwide and kill his opponent, the Dajjal.
This means at the spiritual level that he frees mankind from the yoke of rationality and guides to an intuitive perception that comes directly from God and does not represent a reflection of reality.
Realizing Islam means surrendering oneself to God. All actions are in harmony with divine will and law. The highest realization of Islam is to become an arif bi'llah , a knower through God (often falsely put as knower of God). One can see what comes from God and what a reflection is. One becomes a vessel for divine will and action.
My slave keeps on coming closer to Me through performing Nawafil (doing extra deeds besides what is obligatory) till I love him, so I become his sense of hearing with which he hears, and his sense of sight with which he sees, and his hand with which he grips, and his leg with which he walks. [Al-Buchari 8.509]
Ultimately, He guides the chosen people to their destiny: They overcome the illusion of the mirror but keep their consciousness and are thus enabled to see the glory of God in the hereafter while He will be covered from the sight of the disbelievers.
Narrated Abu Sa`id Al-Khudri: We said, "O Allah's Apostle! Shall we see our Lord on the Day of Resurrection?" He said, "Do you have any difficulty in seeing the sun and the moon when the sky is clear?" We said, "No." He said, "So you will have no difficulty in seeing your Lord on that Day as you have no difficulty in seeing the sun and the moon (in a clear sky)." [Al-Buchari 9.532.2]
So did Allah convey the inspiration to His Servant what He (meant) to convey. The heart in no way falsified that which he saw. Will ye then dispute with him concerning what he saw? For indeed he saw him at a second descent, Near the Lote-tree beyond which none may pass: Near it is the Garden of Abode. Behold, the Lote-tree was shrouded (in mystery unspeakable!) (His) sight never swerved, nor did it go wrong! For truly did he see, of the Signs of his Lord, the Greatest! [An-Najm 10-18]
Appendix: The black banners from Khurasan
The Bible says that the Jews will conquer the Holy Land that God has promised them. Muslims think this is a misconception because they are sure that Islam will ultimately be victorious. Something explains why both might be right: the black banners coming from the East!