Baldur (Scand.). The “Giver of all Good”. The bright God who is “the best and all mankind are loud in his praise; so fair and dazzling is he in form and features, that rays of light seem to issue from him (Edda). Such was the birth-song chanted to Baldur who resurrects as Wali, the spring Sun. Baldur is called the “well-beloved”, the “Holy one”, “who alone is without sin”. He is the “God of Goodness”, who“shall be born again, when a new and purer world will have arisen from the ashes of the old, sin-laden world (Asgard)”. He is killed by the crafty Loki, because Frigga, the mother of the gods, “while entreating all creatures and all lifeless things to swear that they will not injure the well-beloved”, forgets to mention “the weak mistletoe bough”, just as the mother of Achilles forgot her son’s heel. A dart is made of it by Loki and he places it in the hands of blind Hödur who kills with it the sunny-hearted god of light. The Christmas misletoe is probably a reminiscence of the mistletoe that killed the Northern God of Goodness.
Source: H.P.Blavatsky - The Theosophical Glossary