Part of the main quest for Torchlight II seems out of place at first as you may or may not have encountered the very first robotic part in Act One. At first it is very cryptic since it doesn’t give you any clue as to where to look for said Robotic Parts, just the items you’ve gained so far and their respective descriptions.

Fortunately, they’re easy to spot and I’ve listed them here for easy reference.

ACT I

• Side quest: Little Lost Ones (light all the Brazier’s)
  Dungeon: Widow’s Veil
  Region: Crows Pass
  Part located: on the left side of the exit area a passage will open.

ACT II

• Side quest: (Hit all the Gongs around the room.)
  Dungeon: Tower of the Moon
  Region: Ossean Wastes(south end of town)
  Part Location: to the right side of the exit area.
• Side quest: Shadow of Skara
  Dungeon: the Blood Hive (second floor)
  Region: Salt Barrens (north side of town, second zone up)
  Part Location: right side of exit break all the eggs.

ACT III

• Quest related: This is part of the main quest.
  Dungeon: Abandoned [cursed] Windmill.
  Region: Blightbogs (south exit from town)
  Part location: Read all diaries and release the 4 skeletons attached to wooden beams by axes. When all is done a door will open on the west side of the main map area. You have to collect this before teleporting to the boss, otherwise you have to enter the area again.
• Quest Related: Second side quest in the quests given by/for Cacklespit
  Dungeon: Cacklespit Realm
  Region: Sundered Battlefield (north exit from town, second zone up)
  Part Location: Destroy all tree stumps in the zone, You will trigger a log bridge to be created in the center of the map leading to the north.

Finally, to put the robot together you’ll simply need to go through the last quest before unlocking the 4th and final act.  This quest will require you to find the Powersource.  After obtaining it, simply return to town and talk to Dr. Stoker.  The robot will then be rebuilt and will allow you to continue with the game.