Baldgar has come up with an escape plan, and he wants you to use your relative freedom of movement within Isengard to help him carry it out.
'Acca will tell us the location of the secret way out of the Ring, but we will need two things: a way out of these cells and a large enough distraction to keep the Uruk-hai occupied once we reach the surface.
'When Fâsh took me from my cell to work, I saw some of Saruman's experiments. One of these involved a black powder that, when set aflame, caused a tremendous roar and smoke. Some of the machinery seems to spew this powder. If you can collect enough of it, we could use it for our distraction.
'Your relative freedom of movement can help us here, ${PLAYER}, but you must still keep up appearances. Do not let the Uruk-hai know what you are up to! Report to Sagrúrz by the forges and do his work in addition to collecting the powder for me.'
Sagrúrz is by the forges in the main cavern beneath Isengard.
Baldgar wants you to do the work Sagrúrz asks of you, but while you are doing that, he also wants you to collect some black powder.
Weapons are scattered around the floor near the forges. Sagrúrz wants you to pick them up and put them back in an empty barrel. Meanwhile, Baldgar wants you to collect some of the black powder that spews from the works and collects on the floor.
The empty barrel is near the forges in the main cavern beneath Isengard.
Sagrúrz wants you to put the scattered weapons you collected in an empty barrel.
Sagrúrz is waiting to speak with you by the forges in the main cavern beneath Isengard.
Baldgar is in the dungeons below Isengard.
You have stolen some black powder and should bring it to Baldgar.