Short answers, pulled from the story.
Saaremaa is the largest island in Estonia, located in the Baltic Sea south of Hiiumaa and northwest of the Gulf of Riga. It forms the main barrier between the Gulf of Riga and the Baltic Sea, with the Irbe Strait running to its south.
Kaali is a group of nine meteorite craters on Saaremaa. The largest is 110 m in diameter, 22 m deep, and contains Lake Kaali. The impact released roughly 80 TJ of energy, comparable to the Hiroshima bomb, and burned forests within a 6-km radius.
The name Ösel derives from the Old Norse Eysýsla, meaning 'the island district,' used in Icelandic sagas and early medieval Scandinavian sources. Variants of that name appeared in Danish, German, Swedish, and Latin until the first half of the 20th century.
Medieval islanders of Saaremaa, sometimes called the Eastern Vikings, conducted raids across the Baltic region. The Chronicle of Henry of Livonia describes a fleet of sixteen ships and 500 Osilians ravaging southern Sweden, and the 1187 attack on the Swedish town of Sigtuna is among the most noted raids attributed to them.
Louis Isadore Kahn, born in 1901, came from Saaremaa and became one of the most influential architects of the mid-20th century. Fabian Gottlieb von Bellingshausen, born on the island in 1778, led the second expedition to successfully cross the Antarctic Circle.
In 1946, Soviet military authorities declared Saaremaa a restricted zone closed to all non-local civilians, including mainland Estonians and foreigners. The restriction remained in place until 1989, and Estonia regained full independence in August 1991.