"Zoroaster was thus the first to teach the doctrines of an individual judgment, Heaven and Hell, the future resurrection of the body, the general Last Judgment, and life everlasting for the reunited soul and body. These doctrines were to become familiar articles of faith to much of mankind, through borrowings by Judaism, Christianity and Islam; yet it is in Zoroastrianism itself that they have their fullest logical coherence ..." (Mary Boyce, Zoroastrians, pg. 29)
According to Zoroastrian scripture, the end of the world will come about when a comet, called Gochihr, strikes the earth. Its "fire and halo" will melt all metals and minerals and will burn up the world in a general conflagration. The resulting boiling flood of metal will flow over the earth like a river. The righteous, as well as the wicked souls (released from hell) will pass through it. The wicked will be purified of their sins, but the pious will feel like they're passing through warm milk. The most detailed description of this is found in the 30th chapter of the Bundahishn.
Frashegird (Av. "Frasho-kereti" literally making wonderful) refers to the renovation of the universe, the last judgment. The exact date of Zarathushtra is uncertain, but was probably around 1000-1200 BCE.
Righteousness is so worthy and great and valuable, that in one place it is revealed that Zarathushtra asked Ohrmazd: "How much time remains until the time of Frashegird, that is the making of Frashegird and the Future Body?" Ohrmazd said: "3,000 years." Zarathushtra was afraid and said: "A long time remains!" Ohrmazd said: "Then do not let this time seem long to you, for so long as the souls of the righteous are in Garothman, then this much time of 3,000 years will seem in their sight as long a period and as easy as when a comely maiden of 15 years and a young man of 20 years come with one another to their house and sleep upon their soft quilts, and the young man loves the girl with all his soul, and for them that (alone) is required: 'May night never become day!'
"So for those also who are righteous, for them on account of the pleasure and peace which is theirs in Garothman, then for them that (alone) is required: 'May that time never come!'" (From Pahlavi Rivayat, ch. 25. based on tr. of A.V. Williams, 1990.)
In his Gathas (Hymns), Zarathushtra tells us of The World Savior, Saoshyant (Pahl. Soshyant), who is to come and stop the cruelty of bloodthirsty and wicked people, and renew the world, and end death. See Yasna 48.11-12, Yasna 43.3, The victorious Saoshyant and his helpers make the world wonderful: Yt19.9+, Yt19.88+, Astvat-ereta rises out of lake Kansaoya, and Asha will conquer the Druj: Yt19.92+, Dk3.102, Dk3.407.
Three saviors will be born of virgins miraculously impregnated with Zarathushtra's seed while bathing in Lake Kansaoya: Aushedar, Aushedar-mah, and the Saoshyant (named Astvat-ereta).
After that time when Zarathushtra came to a consultation with Ohrmazd, and 1,500 years after the time of Zarathushtra, when it is the millennium of Religion, Aushedar will come into consultation with Ohrmazd for 50 years.
On the same day Mihr Yazad, that is, the sun, will stand at mid-day, for ten days and nights it will stand at the zenith of Heavens.
The (members of the) wolf species will all go to one place, and in one place they will be merged, and there will be one wolf whose breadth (will be) 415 paces and length 433 paces.
And on the authority of Aushedar they [i.e. the Mazda-worshippers] will muster an army, and they will go to battle with that wolf.
After 400 years there will be the Malkosan rain. When it is the time for that rain, (in) the first year the upholders of Religion will say to people: "Store provisions, for there will be rain"; people will store provisions.
Those provisions which they have stored previously will not be required for ten winters, and they will not store provisions any more, and (in) that year there will be rain.
And then Ashawahist will cry out (from) above, and will speak thus: "Do not kill those beneficent animals any more as you have killed them (up to) now! For the beneficent animals will come to maturity so (slowly) that henceforth they will dwindle away. Do not kill (them)!"
At the end of the millennium, Aushedar-mah will come in to consultation with Ohrmazd for 30 years. The sun will stand at the zenith from that day for 20 days and nights.
Other Prophecies (from Zand-i Vohuman Yasht)
There will be seven ages, called the golden age, the silver age, the copper age, the brass age, the lead age, the steel age, and the iron age.
By the winter of the tenth century, crops will not yield seed, plants will be small, people will be stunted and lack skill or energy.
All people will worship greed and be of false religion. They become fat of body and hungry of soul.
Clouds and fog will darken the whole sky. A hot wind and a cold wind will come and carry off all fruits and grain. The rain will not fall at its due time.