The Arhu SparkMaster 5000 is a boss in Divinity: Original Sin
You fight it during the quest Arhu's Failed Experiment
You get the quest from Arhu in Cyseal
You will also trigger that quest just by entering the Rank Tunnel during the quest The Fabulous Five
Victor, Richard, and Visco help you fight it.
You can use Arhu's Arhu SparkMaster 5000 Universal Controller to against the robot - see the Instruction Manual for all possible combinations. Note that using some of the options on the remote control will cause no loot to drop, so you should use it only if you are having problem defeating the automaton.
The SparkMaster controller can be found at Arhu's Study in the Legion Headquarters in Cyseal