Warden Page 328 (Patreon)

The Prisoner's shackles prevent him from using his spells. They have the adding negative of affecting the mana around him. He deflected and blocked spells when they were firing at him earlier. Now he is using it to drain the mana fueling Insight's fires and soon the shield spells containing him will fall. He is confident in his victory and he didn't even need to use all of his cards he brought to the table.