The elves were the first beings to evolve to the point of having an actual civilization. It was they who first learned to tap into the magical power of creation, which some say they stole from the gods themselves. The god Keyldynan became intrigued by these creatures and gave them immortal life if they promised to protect the world and all its inhabitants. The elves took their oath seriously, and they aimed to protect and enlighten the lesser beings on Pallis.
After being the caretakers of Pallis for unknown millenia, the elves realized that their rearing of the lesser beings had been a mistake. The other races used the gods' magic recklessly, seeking to gain power for power's sake. With one last forlorn look upon Pallis, the elves left for the northern continent of Faerstice. There they became isolated from the other races and formed their own kingdoms. The elves lived in enlightened peace on Faerstice for centuries, until the Humbling occured.
After the Exodus, the majority of the elves fled to hidden areas of Faerstice to plan their vengeance against the interlopers. These elves strike out against the other races whenever they can, and they have been responsible for some of the worst calamities in the last four centuries. However, two groups of elves refused to leave the company of the other races.
The oathbreaker elves [high elves in the phb] are elves who resigned themselves to the fate of Faerstice. They gave up on their oath to Keyldynan and integrated themselves into the new society forming around them. By giving up their oath, they also lost their immortality, but they still live for nearly 800 years. Elves still loyal to Keyldynan despise these oathbreakers and will kill them whenever an opportunity presents itself. The other races also hate the elves, as they blame them for all the destruction that is wrought by the loyal elves of Keyldynan; they are also hated because of their natural affinity to magic. This hatred requires due diligence when travelling among the cities of Faerstice, and many oathbreaker elves become masters of disguise out of necessity. Regardless, oathbreaker elves seek to live their own lives by no code other than their own. It is exceedingly rare to find an oathbreaker elf who worships any deity.
Wild elves [wood elves in phb] chose a different route. When they saw the destruction of their homelands, they went feral and chose to rail against everyone, the gods included. Wild elves reverted to their primal ways, and they lost their immortality in the process. They live in close-knit communities within the Deep Wards and keep to a nomadic lifestyle. Their goal is to slaughter anyone who dares to come into their realm. Wild elves rely on the primal magics of nature that their ancestors utilized. As such, many of them wield powerful druidic magics to annihilate any who threaten their way of life. The human kingdoms have open bounties on wild elves, and a clutch of their ears can earn adventurers a good income. Many oathbreaker elves have lost their lives because of this, but not many are concerned about those situations. Encountering a wild elf usually means a fight, but there is a small cult of wild elves who are dedicated to educating the other races about living in harmony with the natural world. Typical wild elves worship no god, but a small number still worship Keyldynan, even though he stripped them of eternal life.