Though stunted and twisted like most of the Noegyth Nibin, Mîm had rather more pride than his brethren. When Túrin Turambar's men captured him, as is recounted in the history above, and tied ropes around his ankles, the Petty-dwarf withdrew his promise to lead the outlaws to his hidden halls. The shame of the bonds made him willing to risk death rather than conciliate his captors. Only the force of Túrin's will compelled Mîm to bring the wanderers to the halls beneath Amon Rûdh.
Túrin's oath to pay a ransom of gold for Mîm's son, slain by an outlaw's arrow, caused the Petty-dwarf to compare the Man to a Dwarf-lord of old. Through the long autumn storms, his respect for Túrin grew into liking, and he shared much of the lore of his people. All that changed when Beleg Cúthalion joined them at Bar-en-Danwedh. Mîm felt the typical Petty-dwarven hatred for Elves, and his regard for this new Mannish friend suffered with the discovery that Túrin's closest comrade was a Sinda. Worse, Túrin ceased to spend his evenings with Mîm in favor of discussion with Beleg.
When Orcs captured Mîm in the spring, his scorn for Túrin's friendship with Beleg made the Petty-dwarf less reluctant to betray the location of Bar-en-Danwedh. And when the Orcs were gone from the bloody hill-top, leaving only the Petty-dwarves and Beleg alive, Mîm raised Beleg's own sword to slay the wounded Elf. He did not succeed and fled howling.
Mîm's pride had one more foray before his death. While dwelling in ruined Nargothrond after Glaurung the Dragon had left its caverns, the Petty-dwarf challenged Húrin, Túrin's father, at the threshold, claiming the Elven hold as his own. Húrin chastized Mîm and reminded him that Túrin, whom the Petty-dwarf had betrayed, had slain Glaurung. Mîm died of his pride, cut down by the stroke of the enraged Húrin's sword.