Samaritanism

The Samaritan religion, also known as Samaritanism, is the national religion of the Samaritans. The Samaritans adhere to the Samaritan Torah, which they believe is the original, unchanged Torah, as opposed to the Torah used by Jews. In addition to the Samaritan Torah, Samaritans also revere their version of the Book of Joshua and recognize some Biblical figures, such as Eli.
Samaritanism is internally described as the religion that began with Moses, unchanged over the millennia that have since passed. Samaritans believe Judaism and the Jewish Torah have been corrupted by time and no longer serve the duties God mandated on Mount Sinai. Jews view the Temple Mount as the most sacred location in their faith, while Samaritans regard Mount Gerizim as their holiest site.
History.
Samaritanism holds that the summit of Mount Gerizim is the true location of God's Holy Place, as opposed to the Foundation Stone on the Temple Mount as Judaism teaches. As such, Samaritans trace their history as a separate entity from the Jews back to the time of Moses, where they believe Joshua laid the foundation for their temple. Samaritan historiography traces the schism itself to the High Priest Eli abandoning Moses' Tabernacle in favor of Mount Gerizim following Joshua's death.
Abu l-Fath, who in the 14th century wrote a major work of Samaritan history, comments on Samaritan origins as follows:
A terrible civil war broke out between Eli son of Yafni, of the line of Ithamar, and the sons of Pincus (Phinehas), because Eli son of Yafni resolved to usurp the High Priesthood from the descendants of Pincus. He used to offer sacrifices on an altar of stones. He was 50 years old, endowed with wealth and in charge of the treasury of the Children of Israel. ...
He offered a sacrifice on the altar, but without salt, as if he were inattentive. When the Great High Priest Ozzi learned of this, and found the sacrifice was not accepted, he thoroughly disowned him; and it is (even) said that he rebuked him.
Thereupon he and the group that sympathized with him, rose in revolt and at once he and his followers and his beasts set off for Shiloh. Thus Israel split in factions. He sent to their leaders saying to them, "Anyone who would like to see wonderful things, let him come to me." Then he assembled a large group around him in Shiloh, and built a Temple for himself there; he constructed a place like the Temple (on Mount Gerizim). He built an altar, omitting no detail—it all corresponded to the original, piece by piece.
At this time the Children of Israel split into three factions. A loyal faction on Mount Gerizim; a heretical faction that followed false gods; and the faction that followed Eli son of Yafni in Shiloh.
Further, the "Samaritan Chronicle Adler", or New Chronicle, believed to have been composed in the 18th century using earlier chronicles as sources, states:
The traditional Jewish narrative of 2 Kings and Josephus, has it that the people of Israel were removed by the king of the Assyrians (Sargon II) to Halah, to Gozan on the Khabur River and to the towns of the Medes. The king of the Assyrians, we are then told, then brought people from Babylon, Kutha, Avah, Emath, and Sepharvaim to settle in Samaria. Because God sent lions among them to kill them, the king of the Assyrians sent one of the priests from Bethel to teach the new settlers about God's ordinances. The eventual result was that the new settlers worshiped both the God of the land and their own gods from the countries from which they came. 
Modern genetic studies (2004) suggest that Samaritans' lineages trace back to a common ancestor with Jews in the paternally-inherited Jewish high priesthood (Cohanim) temporally proximate to the period of the Assyrian conquest of the kingdom of Israel, and are probably descendants of the historical Israelite population, albeit isolated given the people's reclusive history. This casts doubt into, if not totally disproves, this historical theory that Samaritans originated from Assyria.
Furthermore, the Dead Sea scroll 4Q372, which recounts the hope that the northern tribes will return to the land of Joseph, remarks that the current dwellers in the north are fools, an enemy people, but does not explicitly refer to them as foreigners. It goes on to say that these people, the Samaritans, mocked Jerusalem and built a temple on a high place (Gerizim) to provoke Israel.
Conflicts between the Samaritans and the Jews were numerous between the end of the Assyrian diaspora and the Bar Kokhba revolt. Jewish historiography describes multiple instigations from the Samaritan population against the Jews and disparages them, and Jesus' Parable of the Good Samaritan also gives evidence of conflict. The destruction of Mount Gerizim's Samaritan temple is attributed to the High Priest John Hyrcanus.
Following the failed revolts, Mount Gerizim was rededicated with a new temple, which was ultimately again destroyed during the Samaritan revolts. Persecution of Samaritans was common in the following centuries.
Beliefs.
The principal beliefs of Samaritanism are as follows:
Festivals and observances.
The Samaritans preserve the proto-Hebraic script, conserve the institution of a High Priesthood, and the practice of slaughtering and eating lambs on Passover eve. They celebrate Pesach, Shavuot, Sukkot but use a different mode from that employed in Judaism in order to determine the dates annually. Yom Teru'ah (the Biblical name for "Rosh Hashanah"), at the beginning of Tishrei, is not considered a New Year as it is in Rabbinic Judaism.
Passover is particularly important in the Samaritan community, climaxing with the sacrifice of up to 40 sheep. The Counting of the Omer remains largely unchanged; however, the week before Shavuot is a unique festival celebrating the continued commitment Samaritanism has maintained since the time of Moses. Shavuot is characterized by nearly day-long services of continuous prayer, especially over the stones on Gerizim traditionally attributed to Joshua. 
During Sukkot, the sukkah is built inside houses, as opposed to outdoor settings that are traditional among Jews. Samaritan historian Benyamim Tsedaka traces the indoor-sukkah tradition to persecution of Samaritans during the Byzantine Empire. The roof of the Samaritan sukkah is decorated with citrus fruits and the branches of palm, myrtle, and willow trees, according to the Samaritan interpretation of the four species designated in the Torah for the holiday.
The restrictions of Yom Kippur are more universal in Samaritanism, with even breastfeeding and the feeding of children being disallowed.
Religious texts.
Samaritan law differs from Halakha (Rabbinic Jewish law) and other Jewish movements. The Samaritans have several groups of religious texts, which correspond to Jewish Halakha. A few examples of such texts are: