The word "Medieval" refers to the Middle Ages, that period of European history which falls roughly between the fall of the western Roman Empire (A.D. 500) and the fall of Constantinople in 1453. Some scholars would place the beginning of this era as A.D. 1100, and refer to the earlier part of it (between the fall of the Romans to A.D. 1100) as the Dark Ages. The end of the Middle Ages would, in turn, witness the birth of the Renaissance.
Be that as it may — who could quibble over a few hundred years in a place with such a long history — the fall of the Romans in the West gave rise to the emergence of separate kingdoms and monarchs, as well as an increased power of the Roman Catholic Church.
In Scotland, in the early Middle Ages, between the fall of the Romans and the Kingdom of Alba in A.D. 900, two of the most important of the emerging (4) petty kingdoms were those of the Picts and the Scots..
The Vikings arrived in the eighth century, and established colonies along the coasts and islands. In the ninth century, the Picts and the Scots combined under the House of Alpin to form the basis of the Kingdom of Scotland.
The picture above is of the Monymusk Reliquary which dates to the 8th century A.D. It resides in the Museum of Scotland in Edinburgh. It was used for saintly assistance by Scots in battle, much as the Ark of the Covenant was used in battle by the early Hebrews. The Reliquary is now empty.