Heimdall has been shown as having wisdom, being described as 'kind of counsel' in poetry and has provided sage advice to the other gods in the Lay of Thrym, regarding the recovery of Thor's hammer Mjollnir from the Frost Giants. Here too he is credited with the ability to read the future.
Heimdall is the son of Odin, Ruler of the Gods of Asgard, and Alti, daughter of the ancient sea-god, Aegir. Aegir was of a generation of gods older than the Aesir and the Vanir. While Odin was visiting him, he encountered the daughters of Aegir asleep on the beach at Hlesey and stayed the night with them. Falling in love with each of them, he married each of them, and from among them, two children were born, Heimdall and Sif. The nine wave maidens were reported as nurturing Heimdall and Sif on the strength of the earth, the moisture of the sea and the heat of the sun. As an added attribute to this mystical up-bringing, Heimdall grew to be tall and handsome with a dazzling smile of sunshine and inherited incredible senses above that of any other Asgardian. Both Heimdall and Sif thrived so well on this diet that they headed to Asgard to be counted among the gods. The thunder-god, Thor, accepted Sif as his bride, and Heimdall was entrusted with his incredible senses to standing sentry at Bifrost, the rainbow bridge connecting Asgard to Earth.
Since accepting the noble task of guarding and protecting Asgard, Heimdall has never left his post at Bifrost. He also proved to be the cleverest of the gods. He came up with the means for Thor to retrieve his stolen hammer from the giant Thrym who had taken it and even pursued Loki, matching him for each animal form he became while trying to escape, after the theft of Freia's necklace. However, prophecies eventually became known connecting Ragnarok, The Twilight of the Gods, to the death of the god Balder, the most beloved among the gods of Asgard. Loki masterminded these prophecies to come to pass and Balder died as a result. Heimdall faced off against Loki at Ragnarok where they slew each other in combat.
Heimdall as well as the Asgardian gods were restored to life sometime later in what is now believed to be repeating cycles of Ragnarok for the Asgardians. In this new incarnation, Heimdall seems to have no memories of Odin as his father except for the knowledge of Sif as his sister. Odin sent him to earth to investigate if the children of Ask and Embla still survived. Ask and Embla were two mortals who survived the Asgardians' war with the Giants of Jotunheim millennia before. On Earth, Heimdall disguised himself as a mortal man and encountered separately three sets of couples; each of whom treated him with extreme hospitality and courtesy. Each couple had a child nine months after Heimdall's stay who grew up to exhibit the greatest qualities of their families. To one of these children, Heimdall showed the secrets of the runes and wisdom over good and evil so that mortals could become aware of their own destinies.
Returning to his duties at Bifrost, Heimdall has exhibited extreme diligence in his responsibilities to Asgard even to proving to be almost a match against Thor at times although he has also proved extremely loyal in his responsibilities to Odin, Thor and even Frigga. After the Third Host of the Celestial, Heimdall participated with the goddesses of earth to seek out twelve individuals as close to genetic potential to serve as example of human potential. These individuals became known as the Young Gods. Heimdall also showed great compassion toward Amora the Enchantress after the death of her lover, Skurge the Executioner, and she fell in love with him in return. Heimdall, however, was slain during war against the Egyptian god Seth invading Asgard and Amora showed great remorse upon his death. Heimdall was eventually restored to life by Odin but the ordeal with Seth had left him greatly weakened. He chose Heimdall to behold the Odin-Force in his absence as he withdrew to his needed Odin-sleep. One of Heimdall's first tasks was to restore the shattered Rainbow Bridge Bifrost broken by Seth. (Source: angelfire.com)