Answer
John of Antioch played a pivotal role in convening and leading the counter-council in Ephesus in 431, aiming to overturn the decisions of the original Council of Ephesus. This alternate assembly, often referred to as the "Robber Council," successfully exonerated Nestorius, who was accused of heresy for distinguishing between the divine and human natures of Jesus, and conversely, deposed Cyril of Alexandria, a staunch opponent of Nestorius.