Short answers, pulled from the story.
The Marcomannic Wars were a series of conflicts fought from about AD 166 until 180 between the Roman Empire and principally the Germanic Marcomanni and Quadi and the Sarmatian Iazyges, along with several other peoples along the Danube frontier. They occupied the major part of the reign of Emperor Marcus Aurelius.
Yes. Led by the Marcomannic king Ballomar, a coalition of Germanic tribes crossed the Danube, defeated a Roman force of 20,000 near Carnuntum, destroyed Oderzo, and besieged Aquileia in northern Italy. It was the first hostile incursion into Italy since the Cimbri invasion of 101 BC.
Marcus Aurelius began writing his philosophical work Meditations during his campaigns against the Germanic and Sarmatian peoples in the Marcomannic Wars.
During the 173 AD campaign against the Quadi, the surrounded Legio XII Fulminata was saved by a sudden storm. Cassius Dio attributed the event to an Egyptian magician invoking Mercury, while Christian writers including Tertullian credited Christian soldiers' prayers.
The Iazyges surrendered in 175 AD. Their king Zanticus returned 100,000 Roman prisoners and provided 8,000 cavalry auxiliaries, of whom 5,500 were dispatched to Britain. In recognition, Marcus Aurelius adopted the title "Sarmaticus."
After the wars, Rome stationed 16 of its 33 legions along the Rhine and Danube, committing half its total military strength to defending that frontier. Germanic settlement in Dacia, Pannonia, Germania, and parts of Italy also increased significantly, requiring new administrative measures.