 Finn pursues Flame Princess ( voiced by Jessica DiCicco ) , trying to explain to her that he does not want to hurt her . However , Flame Princess , confused by Finn 's aversion to fire , assumes that he merely wants to taunt her . She ventures to the Goblin Kingdom , intent on turning it into her new domain . Finn and Jake , meanwhile , return to the tree fort and , with the help of N.E.P.T.R. ( voiced by Andy Milonakis ) , build flame @-@ retardant battle robots . 
