Perun (Cyrillic: Перýн) is the highest god of the pantheon and the god of sky, thunder, lightning, storms, rain, law, war, fertility and oak trees. His other attributes were fire, mountains, wind, iris, eagle, firmament (in Indo-European languages, this was joined with the notion of the sky of stone, horses and carts, weapons (hammer, axe (Axe of Perun), and arrow), and war. He was first associated with weapons made of stone and later with those of metal.
In Slavic mythology, much like in Norse and Baltic mythologies, the world was represented by a sacred tree, usually an oak, whose branches and trunk represented the living world of heavens and mortals, whilst its roots represented the underworld, i.e. the realm of the dead. Perun was the ruler of the living world, sky and earth, and was often symbolised by an eagle sitting on the top of the tallest branch of the sacred tree, from which he kept watch over the entire world. Deep down in the roots of the tree was the place of his opponent, symbolised by a serpent or a dragon: this was Veles, watery god of the underworld, who continually provoked Perun by creeping up from the wet below up into the high and dry domain of Perun, stealing his cattle, children, or wife. Perun pursued Veles around the earth, attacking him with his lightning bolts from the sky. Veles fled from him by transforming himself into various animals, or hiding behind trees, houses, or people; wherever a lightning bolt struck, it was believed that this was because Veles hid from Perun under or behind that particular place. In the end, Perun managed to kill Veles, or to chase him back down into his watery underworld. The supreme god thus reestablished order in the world, which had been disrupted by his chaotic enemy. He then returned to the top of the World tree and proudly informed his opponent down in the roots "Well, there is your place, remain there!" (Ну, там тваё мейсца, там сабе будзь!). This line came from a Belarusian folk tale. To the Slavs, the mythological symbolism of a supreme heavenly god who battles with his underworldly enemy through storms and thunder was extremely significant.
While the exact pantheon characterization differed between the various Slavic tribes, Perun is generally believed to have been considered as the supreme god by the majority, or perhaps by nearly all Slavs, at least towards the end of Slavic paganism. The earliest supreme god was probably Rod; it is unclear precisely how and why his worship as the head of the pantheon evolved into the worship of Perun. Another candidate for supreme deity among at least some Slavs is Svarog.
Poseidon (/pəˈsaɪdən, pɒ-, poʊ-/; Greek: Ποσειδῶν, pronounced [poseːdɔ̂ːn]) was one of the Twelve Olympians in ancient Greek religion and myth, god of the sea, storms, earthquakes and horses. In pre-Olympian Bronze Age Greece, he was venerated as a chief deity at Pylos and Thebes He had also the cult title "earth shaker". In the myths of isolated Arcadia he is related with Demeter and Persephone and he was venerated as a horse, however it seems that he was originally a god of the waters. He is often regarded as the tamer or father of horses and with a strike of his trident, he created springs which are related with the word horse. His Roman equivalent is Neptune.
Poseidon was protector of seafarers, and of many Hellenic cities and colonies. Homer and Hesiod suggest that Poseidon became lord of the sea following the defeat of his father Cronus, when the world was divided by lot among his three sons; Zeus was given the sky, Hades the underworld, and Poseidon the sea, with the Earth and Mount Olympus belonging to all three. In Homer's Iliad, Poseidon supports the Greeks against the Trojans during the Trojan War and in the Odyssey, during the sea-voyage from Troy back home to Ithaca, the Greek hero Odysseus provokes Poseidon's fury by blinding his son, the Cyclops Polyphemus, resulting in Poseidon punishing him with storms, the complete loss of his ship and companions, and a ten-year delay. Poseidon is also the subject of a Homeric hymn. In Plato's Timaeus and Critias, the legendary island of Atlantis was Poseidon's domain.
Athena became the patron goddess of the city of Athens after a competition with Poseidon, and he remained on the Acropolis in the form of his surrogate, Erechtheus. After the fight, Poseidon sent a monstrous flood to the Attic Plain, to punish the Athenians for not choosing him.