Melanchthon and Augsburg
Melanchthon and Eck were appointed as hardliners, whose presence was necessary for the credibility of the proceedings. Melanchthon came with strict instructions not to deviate from the Augsburg Confession or its Apology.
Anthony Lane, Regensburg Article 5 on Justification: Inconsistent Patchwork or Substance of True Doctrine? (New York, NY: Oxford University Press, 2020), 15