The robot parts themselves are not hard to find or obtain you are just required to (mostly) clear out and explore each map carefully.
Widow's Veil in Crow's Pass. You'll need to light all the braziers in the area to open a room on the map that has the robot drums
In the Ossean Wastes rescue Muzaffar, a Zerypheshi general, to open the Tower of the Moon. Hit all the bronze gongs/shields hanging throughout the level (you should hear a "bong" when you hit each one) to open the gate in the back of the cage where you find Duros the Blade. You'll find the Robot Arm in the center of the small cave at the end of the short corridor.
In the Salt Barrens, once you have demo'd the three infected hives, enter the Brood Hive and clean it out. Make sure, by checking your map, that you have mapped the entire dungeon before leaving. There is small corridor that leads back further, full of eggs (experience and loot), and ends in a small cave where you will find the Robot's Pipes.
When exploring the Sawmill in the Blightbogs area remove all the skeletons that are impaled onto post throughout the map. This should unlock a once locked gate in the area containing the Robotic Body. Also the book are awesome to read so just do that too.
While in Craklespit's Realm during act 3 you'll be able to see the Robot Head (or another part) up on a ledge at the very top right hand side of the map. To get to this robot part you will need to clear out the whole map finding tree trunks that spew green fog. Destroy these tree trunks and head from the middle of the map to the northeast you'll hear a chime and tree trunks will float to create a bridge. If you are having trouble finding it just walk along the right hand side of the map after destroying ALL of the tree trunks.
Once you have all the parts take them to Professor Stoker in the Imperial Camp. I don't know if you need to have powered up the robot that opens the door to the Broken Mines or not. Once he had powers up the door robot he comments on the pieces you have in your possession and puts the robot together for you. You end up with the Trill-Bot 4000, a wannabe bard bot. You will get the Three Sisters side quest from him.
Side Quest: The Brave OnesPrevious
Side Quest: Secret of the Ezrohir
Robot Parts is an optional sidequest in Torchlight II that is unlocked as soon as you find the first of five robotic parts. The quest spans all acts in the game, and the pieces can be found in order, or if you skip one you can come back to a previously cleared act (by speaking to the relevant NPC in each town) and find missed pieces.
This guide is also available here[www.thesewall.com] (more mobile friendly).
- Found in Widow's Veil, a dungeon in Crows' Pass. In order to open the secret room you have to light all the braziers. The room can then be found near the portal to the surface or back along the middle path through the dungeon.
- Found in the Tower of the Moon, a dungeon in the Ossean Wastes. Hit all of the brass gongs located on the walls of the room to open the door near the rear of the dungeon.
- Found in the Brood Hives, which is located in the Swarm Point area of the Salt Barrens. Destroy all the roach eggs to reveal the secret area.
- Found in the Abandoned Sawmill, which is found in the Blightbogs. Unpin the four skeletons found on the walls and trees. Skeleton 1 is found near the Day One journal, Skeleton 2 on the path to the docks, Skeleton 3 on one of the houses near the middle of town, and Skeleton 4 on the path out of town. The gate near the Day Four journal will then open, and the Robotic Body is found within.
- Found in Cacklespit's Realm, a dungeon in the Sundered Battlefield. In order to open Cacklespit's Realm, you need to complete a chain of sidequests, starting with Cacklespit's Brew.
- Cacklespit's Brew is started by finding a bell in the Rot Gardens area of the Blightbogs. You will need to hang the bell on a post, which is on an elevated platform randomly located somewhere in the Blightbogs. After hanging the bell and speaking with Cacklespit to complete the quest, you will need to return to the Imperial Camp to start the next quest.
- Once in the Imperial Camp, speak to Widget, one of the raccoons, to start Fade's Passage. You will need to go to the far western side of the Sundered Battlefield, where Fade will appear after you activate two altars on a hill. After speaking to Fade and completing the quest, he will give you another quest, Cacklespit's Realm.
- Cacklespit's Realm tasks you with finding four skulls located in graves around the Sundered Battlefield. By this point you've probably cleared the battlefield, so gathering them should be fairly easy. On one of the graves you will go through a portal to a survival challenge. Once you collect all four skulls, take them back to Fade, who will provide you transportation to Cacklespit's Realm.
- Once there, you need to destroy all six tree trunks to open the secret path, which is located on one of the islands (the exact one varies). Be warned that once you teleport to the boss island to fight Cacklespit, you will not be able to get back to the other islands without going back to Fade.
Trill-Bot 4000 will then give you a quest called the Three Sisters, which is located in the Sundered Battlefield.
Upon completion of Robot Parts you will receive standard quest rewards in addition to unlocking the achievement The Band Played On.
For completing the Three Sisters, Trill-Bot 4000 will give you a class-specific unique item and 590,000 experience (that's not a typo - check the screenshot).
Additionally, in the course of completing the quest you will get at least one unique socketable and unlock three more achievements.
--> Added some additional info to clarify how to obtain the Robotic Head.
--> Corrected an error in the Rewards subsection and made it more comprehensive.
01/22/2013 - version 1.0