Deities, holy beings: The Trimurti
The Trimurti (three forms) is a Hindu concept which symbolizes the functions that sustain the cyclic creation, preservation and destruction/assimilation of the cosmos. These three functions are personified by the forms of Brahma the creator, Vishnu the maintainer or preserver and Shiva the destroyer or transformer. Nevertheless, these deities are to be understood as three manifestation of a single Absolute Principle, the Brahman.

Foundational myth: Myth of creation from the Brahma Lotus
In Hinduism there is no single story of creation since the world is recreated countless times. In the vast corpus of Hindus myths there is a tremendous variety and variation.
One common theme underling a majority of creation myths is the image of the cosmic lotus in which Brahma is born. Here is one of the most popular variation: in the beginning the entire universe was pervaded by Brahman, the abstract divine force (not to be confused with the Brahma deity!). There was no earth and no heaven. At a particular time a vast ocean washed over the cosmos and a huge serpent emerged from the waters. Then the Supreme deity appeared (in the case of this myth he is Vishnu), sleeping on the serpent. As Vishnu slept, out of his navel grew a lotus. When the lotus opened, Brahma was sitting there. Brahma then set about creating the world. He broke the lotus into three pieces. With the first made the heavens, with the second the skies, and with the third the earth. He then populated the earth with all living beings and the heavens with other gods.
Brahma is thus a secondary deity, being born from a lotus which sprouted out of the navel of a greater sleeping deity. The life of the god Brahma last till Vishnu is asleep. When Vishnu wakes up, Brahma disappears. This remarks the incommensurability between the created world, which contains also heavens were other gods dwell, and the Absolute, the Brahman. In front of the Absolute, the present world is just a minimum lapse. This explains also why Brahma is not commonly a object of worship in Hindu traditions.

Main Doctrinal tenets: concept of cyclic time and division in yuga
Time is cyclical in the Hindu view. The cosmos is created, maintained for a certain period, then destroyed, only to be recreated. This cycle has no beginning and no end. There's a great difference from the linear conception of time in Christianity, where time starts with God's creation of cosmos and end with the Final Judgment or the World to Come.
 Each world cycle (sometimes called a Great Cycle) is the equivalent of a single day in the life of the creator god Brahma. Each Brahma-day lasts 4,320,000 years. Each Brahma-day is divided into four Yugas. The first, the Satya Yuga is said to last about 1.7 million years. This is the "Age of Truth", when humanity is governed by gods, and every manifestation or work is close to the purest ideal. It is sometimes referred to as the "Golden Age". The subsequent ages are said to progress towards deterioration. The second, the Treta Yuga about 1.3 million years; the third, the Dvapara Yuga about 860.000 years. The last, the Kali Yuga, about 430.000 years. The world as we know it is currently in the last of the four Yugas, the Kali Yuga, the most chaotic and degenerated period, when Dharma— the cosmic order—has broken down almost completely.
Brahma, the Creator, is said to live 100 Brahma-years, for a total of 155.520.000.000.000 human years, which is a hyperbolic number to stress the oppressive character of the cycle of rebirth.

Analysis of the sources.
Source 1:.
Trimurti
Image of the three gods of the Trimurti (see above), together with their consorts. Brahma, with his consort Saraswati, is recognizable by his four heads and he holds copies of the oldest Indian sacred scriptures, the Vedas Corpus. Next to him is Vishnu, recognizable by the blue skin and crown, with his consort Lakshmi. To their right Shiva, recognizable by the snake coiled on his neck and the crescent moon on his forehead, together with his wife Parvati. All three divine couples sit on lotus flowers, which are one of the most ancient Indian symbols of purity and spiritual power.

Source n° 2
Myth of the Creation from the  Brahma Lotus
A representation of the Creation myth (see above). Here again, Vishnu is recognizable by the blue skin, the crown and other iconographic elements such as the club, the lotus and the conch shell laid on the serpent. On the right there is Vishnu's consort Lakshimi. Out of the navel of Vishnu grow a lotus flower which contains Brahma, here again recognizable by his four head.

Intercultural & Interdisciplinary information.
(Latin and Greek Literature)
Two classical authors Hesiod and Ovid offer accounts of the successive ages of humanity, which tend to progress from an original, long-gone age in which humans enjoyed a nearly divine existence to the current age of the writer, in which humans are beset by innumerable pains and evils. In the two accounts that survive from ancient Greece and Rome, this degradation of the human condition over time is indicated symbolically with metals of successively decreasing value (gold, silver, bronze, iron).
It is interesting to see how many religious traditions consider the current situation of man as a degradation of a previous joyful existence (for example, the expulsion from Eden).