From Halopedia, the Halo wiki
A religion is a set of tenets and practices, often centered upon specific supernatural and moral claims about reality, the cosmos, and the nature of sapient beings, and often expressed through prayers, rituals, or religious laws. Religion also encompasses ancestral or cultural traditions, writings, history, and mythology, as well as personal faith and religious experiences. The term "religion" refers to both the personal practices related to communal faith and to group rituals and communication stemming from shared conviction.
Daowa-maad and ancient human mythology
Buddhism is a religion and philosophy significant variation in beliefs among its adherents. Buddhism is based on the teachings of Gautama Buddha, sometimes known simply as "The Buddha". All traditions recognize Gautama Buddha as an enlightened teacher who shared his insights in order to help sentient beings end their suffering in accordance with the laws of Karma by understanding the Four Noble Truths; realizing the true nature of phenomena and thereby escaping the cycle of suffering and rebirth known to Buddhists as Saṃsāra. Among the methods Buddhist schools apply towards that goal are ethical conduct, the cultivation of wisdom, the training of one's mind through learning and meditation, altruistic behavior, renunciation of worldly matters, devotional practices and, in some branches, the invocation of holy beings to seek their help in achieving Nirvana.
A Buddhist is one who takes refuge in The Three Jewels: Buddha; one who is Awakened, Dharma; The Teaching (of Buddha), and Sangha; The Community (of Buddhists).
Christianity is a monotheistic religion centered on the life and teachings of Jesus of Nazareth as presented in the New Testament. Its followers, known as Christians, believe that Jesus is the begotten Son of God and the Messiah (Christ) prophesied in the Old Testament. To Christians, Jesus Christ is a teacher, the model of a virtuous life, the revealer and son of God, and most importantly the savior of humanity who suffered, died, and was resurrected to bring about salvation from sin. Christians maintain that Jesus ascended into heaven, and most denominations teach that Jesus will return to judge the living and the dead, granting everlasting life to his followers.
Heathenry is the modern Pagan religion focused on Germanic pre-Christian beliefs, notably those of Scandinavian cultures. Its followers, called Heathens, worship numerous gods (Odin, Thor, Freyja, etc) and venerate their ancestors and spirits of the land (called 'wights', also known as elves/alfar and dwarves). While there is no sacred text per se for Heathenry, writings such as the Prose and Poetic Eddas and the Hávamál are held as important. Heathen holidays focus on the cycle of nature, with the four largest festivals marking cross-quarters of the year; Ostara (Spring Equinox), Midsummer (Summer Solstice), Winter Finding (Autumn Equinox), and Yule (Winter Solsice). Morally, Heathens respect and hold in high regard what are known as the Nine Noble Virtues: Courage, Truth, Honor, Fidelity, Discipline, Hospitality, Self Reliance, Industriousness, and Perseverance.
In the 26th Century, the colony world of Sedra is noted by Lieutenant Michael Horrigan as "still believing in Valhalla". Valhalla, in Norse mythology, is the High Hall of the god Odin, and one of several afterlife destinations in Heathenry; notably for those who have died in combat and are chosen by Odin.
Islam is the Abrahamic religion articulated by the Qur’an, a text considered by its adherents to be the verbatim word of the one, incomparable God, and by the Prophet of Islam Muhammad's demonstrations and real-life examples. Islam literally means "submission (to God)." Muslim, the word for an adherent of Islam, is the active participle of the same verb of which Islām is the infinitive.
Muslims regard their religion as the completed and universal version of a primordial, monotheistic faith revealed at many times and places before, including, notably, to the prophets Abraham, Moses and Jesus. Islamic tradition holds that previous messages and revelations have been changed and distorted over time. Religious practices include the Five Pillars of Islam, which are five obligatory acts of worship. Islamic law touches on virtually every aspect of life and society, encompassing everything from banking and warfare to welfare and the environment.
Triad is a human religion founded by the self-proclaimed spiritual guru Dasc Gevadim. The followers of Triad believe that everyone harbored three internal lives, and believed one could reach spiritual transcendence by linking the three.
Zen is a form of Buddhism that became popular in China and Japan and that lays special emphasis on meditation. According to Charles S. Prebish: "Although a variety of Zen 'schools' developed in Japan, they all emphasize Zen as a teaching that does not depend on sacred texts, that provides the potential for direct realization, that the realization attained is none other than the Buddha nature possessed by each sentient being ..." Zen places less emphasis on scriptures than some other forms of Buddhism and prefers to focus on direct spiritual breakthroughs to truth.
Ancient Sangheili mythology
Believed that modifying forerunner technology would help their race exceed.
Ancient Jiralhanae mythology
The Covenant religion, given no specific name, is a polytheistic religion that centers around the belief that godhood is a state attainable by mortals and that the Forerunner attained such a state through activation of the Halo Array, which sent them on their Great Journey to salvation. Originating as the belief system of the San'Shyuum, it was eventually adopted and, to an extent, modified by the various races that would later join the Covenant, with the most devoted new members being the Sangheili and the Jiralhanae. It would continue even after the end of the Covenant as the Sangheili faith, although modified by recent revelations concerning the true purpose of the Halo Array.
Forerunner belief system
The Forerunner belief system was based on the belief that they upheld the Mantle, the source of Forerunner authority as the stewards of the galaxy. The Forerunners believed that the Mantle had been passed down to them by the Precursors, god-like creatures with the power to travel intergalactic distances and accelerate the evolution of intelligent life.