What I'm about to give you is called seaforium. It is a highly volatile explosive with some unique properties. Due to its malleable nature, you will be able to fill in the hinges and cracks of the cage for maximum damage.
Return to your friend and use the jumbo seaforium charge to set him free.
Let's hope he honors the bargain. He's our only hope.
Do not be afraid, little one. Gymer is an honorable giant. Like you and your people, I too wish to see the Scourge driven away from this land and the Lich King destroyed. I will help you, as promised, to the best of my ability.