Short answers, pulled from the story.
The Scythians were an ancient Eastern Iranic equestrian nomadic people who migrated from Central Asia, originating in the steppes of either present-day eastern Kazakhstan or the Altai-Sayan region of Siberia. They moved to the Pontic Steppe in modern-day Ukraine and southern Russia during the 9th to 8th centuries BC, after being expelled from Central Asia by the Massagetae or the Issedones.
The Scythian triad refers to three categories of distinctive objects: weapons, horse harnesses, and items decorated in the Animal Style art. The discovery of these items in the eastern Eurasian steppe in the 1930s led early modern scholars to apply the label "Scythian" broadly to many nomadic Iron Age cultures, a practice later criticised by specialists like Askold Ivantchik for conflating distinct peoples.
The Scythians supported the Medo-Babylonian coalition that destroyed the Neo-Assyrian Empire, backing the conquests of Aššur in 614 BC, Nineveh in 612 BC, and the last Neo-Assyrian remnants at Harran in 610 BC. Earlier, under king Madyes, the Scythians had imposed hegemony on Media at the request of Ashurbanipal, effectively propping up Neo-Assyrian power for roughly 30 years before switching sides.
The Scythians supplied grain, slaves, cattle, furs, and fish to Greek cities, receiving in return wine, fabrics, metalwork, pottery, and luxury goods. Sedentarised Scythian farmers sold up to 16,000 tonnes of grain to Pantikapaion during the 4th century BC for resale to Athens. Athens also purchased a group of Scythian slaves who served as the city's public police force.
The collapse in the early 3rd century BC resulted from several overlapping pressures: competition from Ptolemaic Egypt undermined the grain trade that sustained the Scythian aristocracy, climatic changes and overgrazed pastures degraded the steppe economy, and the Sarmatians, particularly the Roxolani tribe, seized Scythian pastures from the east. The Scythian capital of Kamianka was abandoned and the material culture of the Scythians disappeared.
The Scythians spoke languages belonging to the eastern branch of the Iranic language family. The western dialect group survived as the medieval language of the Alans and eventually gave rise to modern Ossetian, still spoken in the Caucasus today. The eastern Scythian dialects are related to the Saka languages of Central Asia.
Bede invented a Scythian origin for the Picts in his Historia ecclesiastica gentis Anglorum, exploiting a resemblance between the Latin name for the Irish, Scotti, and the word Scythia. The Irish mythological text Lebor Gabála Érenn elaborated this into a full origin legend, tracing the ancestors of the Gaelic people through Egypt, Moses's parting of the Red Sea, and back to Scythia before a migration via Africa and Spain to Ireland.