Short answers, pulled from the story.
Mycenaean religion refers to the religious beliefs and practices of Mycenaean Greece, roughly 1600-1100 BC. Evidence suggests it was the forerunner of classical Greek religion, sharing divinities such as Zeus, Poseidon, and Dionysus, plus practices like animal sacrifice and votive offerings.
Mycenaean religion existed roughly between 1600 and 1100 BC, several centuries before classical Greek religion, which spanned 510-323 BC. Terms such as theos, hieros, nawos, and temenos survived from the Mycenaean period into classical Greek usage.
Linear B tablets and archaeological finds attest to gods including Poseidon, Potnia, Demeter, Persephone, Artemis, Paean, Athena, and Dionysos, along with Zeus, Hera, Hephaestus, Ares, Hermes, Eileithyia, and Erinya. Aphrodite is notably absent from the surviving Mycenaean record.
Shrine sites associated with Mycenaean cult activity include Lerna, Phylakopi on the island of Milos, Delphi, Dodona, Delos, Eleusis, and Abae. In Crete, several Minoan shrines continued in use into the LMIII period, roughly 1400-1150 BCE.
Mycenaean religion is difficult to reconstruct because no literature beyond simple offering lists survives, and the Linear B tablets mostly just name gods as recipients of goods. Scholars such as John Chadwick, Moses I. Finley, Martin Nilsson, and Thomas G. Palaima have disagreed over how much of it derived from Minoan religion on Crete.
Poseidon, recorded as Po-se-da-o in Linear B, held a place of privilege as a chthonic deity connected to earthquakes, called E-ne-si-da-o-ne, or earth shaker. He also appears to have represented a river spirit of the underworld, similar to figures found in Northern European folklore.