Deities, holy beings: Shiva
Shiva means ("The Auspicious One"), is a popular Hindu deity. Shiva is regarded as one of the primary forms of the Absolute. He is the Supreme God Ishvara (see below) within Shaivism (see below), one of most influential denominations in Hinduism.
Shiva has an extraordinary concordia discords of both terrific and benevolent aspects. One of its antecedents in the Veda Corpus, the sacred texts of Hinduism, is the wrathful deity Rudra. While Rudra was connected with death, Shiva is connected to the idea of destruction and assimilation of the cosmos. But this idea of destruction is to be understood in terms of liberation from the cycle of rebirth. Therefore, the benevolent aspect of Shiva refers to his will of rescuing his devotees from the suffering of rebirth.
At the highest level Shiva is limitless, transcendent, unchanging and formless. In his benevolent aspects, he is depicted as an omniscient ascetic as well as a householder with his wife Parvati and three children, the most famous of them is Ganesha, the elephant-head deity. In fierce aspects, he is often depicted slaying demons representing ignorance.
In particular Shiva is worshiped as the divine archetype of the Yogin, the ascetic practitioner of Yoga, destroyer of the attachment towards the sensual world. This figure of Shiva as Yoga practitioner could date back to 2300–1900 BCE, long before the invasion of Indo-aryans, whose culture originated Hinduism in 1300 BCE.
His iconographic traits are a cobra coiled around his neck or arms, the Yoga posture, and a trident.
Other famous forms in which he is represented are the Narajata (King of Dance), and the aniconic figure of Lingam, a phallic image (see below).

Main doctrinal tenets: the concept of Supreme God or Ishvara
Hinduism is commonly said to be a polytheistic religiosity, but it is should be understood as Henotheism. Henoteism is the belief in and worship of a single god while accepting the existence or possible existence of other deities that may also be worshipped. In the case of Hinduism, a concept of pivotal importance is that of Ishvara (the Lord). The Supreme God is thus the personification of Brahman, the eternal ground of reality, which is behind a world in cyclical flux of birth, development and destruction. Because of this, Ishvara is different from the other deities, which, although being superior to men, are nonetheless subject to samsara and karman (the cycle of reincarnation and the law of deeds' retribution).
Hinduism could be called polytheistic in the sense that there are many different gods—classically there are said to be 330 million! But Hindus often worship a particular form of the god or goddess as the Supreme God, which is also called an Ishtadevata, a chosen or personal god. Some of these forms are pan-Indian, such as Vishnu or Shiva, while others are local, often only known at the regional level.

Main rites: Yoga
Yoga is not technically a ritual. It is a ancient tradition of thought and practice whose origins predate the invasion of the Indo-aryans. The term Yoga encompasses a number of psycho-physical exercises aimed to control the practitioner’s senses and to still the mind in order to gain a state in which the consciousness is no more affected by the inputs coming from a world deemed as illusory (Maya). This in order to experience, inside the purified self, the truth of Atman, the equivalent in each man of the Brahman (the  eternal Absolute beyond a world of change), and attain the liberation from the Samsara, the endless cycle of rebirth.
The particularity of Yoga is its articulated prescriptions of physical nature (exercises, way of sitting, mode of breathing and so on) along with meditative exercise. Upon these prescriptions, various religious thinkers built different theological frameworks in order to fit Yoga to their religious traditions. In fact, Yoga is not a mere gymnastic, as often it is understood in the west, but it should be better understood as the peculiar Indian approach to the Sacred. Virtually any religious traditions include also Yoga techniques in their approaches towards liberation.

Main doctrinal traditions: Shaivaism
Shaivism, is one of the most widely followed sects of Hinduism, which reveres the god Shiva as the Supreme God. Followers of Shiva, called "Shaivists," believe that Shiva is the creator, preserver, destroyer, revealer and concealer of all that is.
It is very difficult to determine the early history of Shaivism. Shaivism in one of the oldest worship of Hinduism, because there is the archaic deity Rudra which is an antecedent of Shiva.
Around 320 - 500 CE Purana texts (see below) developed and Shaivism spread rapidly thanks to the singers and composers of the Puranic narratives.
Shaivists are more attracted to asceticism than adherents of other Hindus sects, and may be found wandering India performing self-purification rituals. They worship in the temple and practice Yoga, striving to be one with Shiva within. Fervent Shiva devotees are identified with three vertical line on their forehead and are often covered in ashes. These ashes serve as a reminder to the believer to cast away selfish and worldly desires that wrap the self in Maya , and calls to mind the legend of how Shiva burned Kama (the god of desire) to ashes when Kama attempted to break Shiva's meditation.

Sacred texts and other main texts: Puranas
The Puranas ("of ancient times") are ancient Hindus texts (composed between 250-1000 CE) eulogizing various deities, primarily the most worshipped deities such as Vishnu and Shiva, through divine stories. Puranas may also be described as a genre of important religious texts, notably consisting of narratives of the history of the universe from creation to destruction, genealogies of kings, heroes, sages, and demigods, and descriptions of Hindus cosmology, philosophy, and geography.
Puranas are text mainly addressed to people who can't access the Vedas, the corpus of Hindus Sacred Texts. Therefore they are written in vernacular language and are disseminated by Brahmin scholars, who read from them and tell their stories.
Puranas, alongside with other texts such as epic, are classified as Smrti ("remembered"), which means that such text are to be passed down to next generations, but also that  there is the possibility (and indeed, the necessity) of adapting them to the variable human circumstances.
This classification differentiate this kind of texts from the Shruti (revelation), that is, the Sacred Texts of the Vedic Corpus, which represent the expression of eternal truths.

Contextualization and analysis of sources
Source n° 1
Dancing Shiva
Iconographic analysis:
A cobra uncoils from his lower right forearm, and the crescent moon and a skull are on his crest. He dances within an arch of flames.
The upper right hand holds a small drum shaped like an hourglass. It symbolizes sound originating creation or the beat of the drum is the passage of time.
The upper left hand contains fire, which signifies destruction. The opposing concepts in the upper hands show the counterpoise of creation and destruction or the fire of life.
The second right hand shows a gesture that means protection from both evil and ignorance to those who follow the righteousness of Dharma, the cosmic order.
The second left hand points towards the raised foot which signifies upliftment and liberation.
The dwarf on which Nataraja dances is a demon which symbolises Shiva's victory over ignorance.
As the Lord of Dance, Nataraja, Shiva performs the the dance in which the universe is created, maintained, and dissolved.
The stoic face of Shiva represents his neutrality, thus being in balance.

Source n° 2
Image of Proto-Shiva
The Pashupati Seal is the name of a steatite seal (dating from 2600–1900 BCE) discovered at Mohenjo-daro, an archeological site in Pakistan. The seal depicts a seated tricephalic figure with a horned headdress surrounded by animals. It is purported to be one of the earliest depictions of the Hindus god Shiva. The seal is named after "Pashupati" (lord of animals), another epithet of Shiva. There is a human figure at the center seated on a platform and facing forward. The legs of the figure are bent at the knees with the heels touching and the toes pointing downwards. The arms extend outwards and rest lightly on the knees with the thumbs facing away from the body. This posture is strikingly similar to a Yoga way of sitting. This evidence explains that antecedents of Shiva's worships and Yoga conception predate the indian invasion of the Indo-aryan civilization (1300 BCE).

Source n° 3
The Linga
The Linga (meaning "mark", "sign") is a representation of the Hindus deity Shiva used for worship in temples. In traditional Indian society the Linga is seen as a symbol of the energy and potentiality of the God.
The Linga is often represented alongside the Yoni, a symbol of the goddess or of Shakti, female creative energy (see sec. 7). The union of Linga and Yoni represents the indivisible two-in-oneness of male and female, the passive and the active force.
The phallic iconography of Linga refers to a myth contained in a Puranic Texs, which narrates of the auto-castration of Shiva, motivated by his refusal to create mankind which will be ultimately doomed to the suffering of rebirth.
Another Puranic texts describes another origin of the Linga as the beginning-less and endless cosmic pillar of fire, the cause of all causes. Lord Shiva is pictured as emerging from this cosmic pillar of fire proving his superiority over other gods.
See also intercultural and interdisciplinary information below.

Intercultural & Interdisciplinary information.
British missionary William Ward criticized the worship of the Lingam (along with virtually all other Indian religious rituals) in his influential 1815 book A View of the History, Literature, and Mythology of the Hindoos, calling it "the last state of degradation to which human nature can be driven", and stating that its symbolism was "too gross, even when refined as much as possible, to meet the public eye." According to some scholars, Ward's book became a centerpiece in the British construction of Hinduism and in the political and economic domination of the subcontinent.
However, the phallic symbol does not refer to fertility or sexuality, as  is common in other religions. On the contrary, as the castration myth explains above, it means the refusal of desire, the will to save humans from suffering and the male energy directed towards ascetic goals.