Dr Fenkenbrain is the living brain of Dr Fenkenstrain in the Dimension of Disaster featured in the 2016 Hallowe'en event. He is found inside the Invention Guild where players can start the 2016 Hallowe'en event.
According to Iron Doc Mk IV, Dr Fenkenbrain was in captivity until the dwarves freed him. Iron Doc doubts Fenkenbrain's work as being "unmoral", though Fenkenbrain responds that the enemies surrounding them have no morals. Fenkenbrain notices the player and has them work for him.
If the player completed Creature of Fenkenstrain quest, the player will already be aware of their power and Fenkenstein gives up, unable to realise how the player already knows about it. Fenkenstein later admits to Iron Doc that he used his ring to persuade the dwarves he was honest. While he managed to trick them, he admits that he still has some honesty left in him.
Fenkenbrain tasks the player with helping to "invent" a god construct to defend Ice Mountain from their enemies, as the dwarves are the only group of liberators in Asgarnia. The god construct would defend the mountain from trolls, goblins, zombies and Kinshra that attacked the mountain. The player defeats the god construct, and Fenkenbrain views this as a failure. Despite not working according to his plan, Fenkenbrain thanks the player and tells them to help him create better constructs.