History and Culture
The Aesir or Asgardians evolved on the world of Asgard about seven million years ago. From here they developed a civilisation from 50,000 years BC that spans almost one hundred worlds densely clustered along a spiral arm on the opposite side of the galaxy from Earth.
The Aesir believe themselves to have been uplifted by some kind of godlike being they refer to as Ymir. It is told that one day they are expected to uplift another race to become new defenders of the galaxy. They also believe all the Universe is part of larger lifeform they call Yndrassil or the world tree.
Their government is under the leadership of a High King who chooses his successor from those he believes are worthy. The successor doesn't have to be related to the high king and can be anyone as long as the successor is deemed able to be a good leader.
In the Humans 12th century the Kalac invaded the Asgardians worlds. Though eventually repulsed, this left a deep routed sense of caution when dealing with other races which has lead to a isolation policy only know being broken by the new High King
Asgard is a world with a dense inner core. This has resulted in a high gravity exerted upon its surface. The local lifeforms have developed to have dense muscle and bone structures to allowe easier movement. The higher concentration of cells in the Aesir has resulted in an increase in the organs a human would call the Pancreas. This means cells are more easily replaced resulting in significently faster healing (as in bones take weeks to heal rather than months, arms are not replaced) and incredibly long lifespans lasting for hundreds of years. The higher muscle structure has meant that freed of the gravity of their homeworld, the Aesir are capable of great acts of strength lifting may time their own body weight.
The Aesir space traval is unique. Though ships are equiped with crude FTL engines, they are slower than the ships of other races due to alternative research yielding better results. The Aesir controlled systems are instead installed with a large sattalite, usually orbiting the colony, called a Bifrost. This sends the ship to the next connecting Bifrost leaving a trail of different spectrums of light in its wake leaving to its more common name of "Rainbow Bridge".
In battle most Aesir disdain long range weapons for close combat and other short range weaponry relying on their advanced armour and dense bone structure to protect them. This doesn't mean they are not armed for space combat or are lacking in energy weaponry, but that they choose to follow their own warrior code in combat rather than rely on "cowardly means of victory"
In general the mysterious manner the Aesir treat their own technology lead many races encountering them for the first kind to view them as wielders of some kind of magic