Finding five robot parts hidden through out the acts in Torchlight 2 will enable you to construct a robot; which in turn will grant you new quests.
Act 1 – Widow’s Veil (Crow’s Pass)
Light up all the braziers throughout the dungeon to open a secret room which contains the first part (Robotic Drum).
Act 2 – Tower of the Moon (Ossean Wastes)
Hit every gong in the dungeon to open a secret room which contains the second part (Robotic Arm).
Act 2 – Blood Hive
You need to crush all the eggs found on the last floor of the dungeon to get the third part (Robotic Pipes).
Act 3 – Abandoned Sawmill
Remove all skeletons from every wall in the dungeon to open a secret room which contains the fourth part (Robotic Body).
Act 3 – Cacklespit’s Realm
This dungeon will be available after completion of a previous quest where you’ll find a bell in the marshlands. Once you have entered in the dungeon, destroy three tree stumps to unlock the secret area which will contain the last part (Robot Head).
Returning the Parts
Take all the parts to Zeryphesh in Act 2 and he’ll construct Trillbot-4000. Speak with him to unlock new and difficult dungeon.