The NME

Hint 1 of 11:

Now THIS is a tough boss.  The NME has mines similar to Krist, fires homing
missiles, and has a flamethrower-like weapon that can toast you in a second.

Hint 2 of 11:

Kill all of the robots in NME's room.

Hint 3 of 11:

Run around until the NME approaches -- you'll hear glass shattering, and the
boss music will play.

Hint 4 of 11:

Look behind the glass that the NME came out of.

Hint 5 of 11:

That iron key is what you need to beat this mechanical monster.

Hint 6 of 11:

It will open up several smaller room with weapons.

Hint 7 of 11:

It will also open a door that leads to an area with lots of Priest Porridge
and Drunk Missiles.

Hint 8 of 11:

Watch out for the Ballistikraft in these rooms, though!

Hint 9 of 11:

Now, run out, try and dodge the shots of the NME, and fire everything.