Short answers, pulled from the story.
Esaias Tegnér is best known for Frithjof's saga, a romantic epic poem published in full in 1825 that made him one of the most celebrated poets in Europe. The work was said to have been translated twenty-two times into English and twenty times into German, and at least once into every European language.
Tegnér was made Bishop of Växjö in 1824, after more than two decades as a lecturer and then professor at Lund University. He remained in Växjö until his death on the 2nd of November 1846.
The Gothic League, known in Swedish as Götiska förbundet, was founded in Stockholm in 1811 as a club of young, patriotic men of letters. Tegnér quickly became its chief figure; the league published a magazine called Iduna and promoted the study of Icelandic literature and old Norse history.
Goethe took up his pen to commend Frithjof's saga to his German countrymen, describing it as an alte, kräftige, gigantischbarbarische Dichtart. He also expressed a wish for Amalie von Imhoff to translate it into German.
Tegnér became moody and melancholy in the 1830s, complaining of fiery heats in his brain as early as 1833. In 1840 he suddenly became insane during a visit to Stockholm and was sent to an asylum in Schleswig; he recovered and returned to Växjö in early 1841. He suffered a stroke of apoplexy in 1843 and died on the 2nd of November 1846.
Longfellow translated Nattvardsbarnen, an idyll Tegnér completed during his years in Lund. The poem was published in 1820 and is considered a secondary work compared to Frithjof's saga.