Obadiah Grimm was a character featured in issue #12 of Sinister. He resembled a skeleton with long black hair and glowing red eyes. As the cover of issue #12 largely proclaimed, "his touch [brought] death".
Some time before 23 December 1972, Walter began having hallucinations of Grimm brought on by the anniversary of his mother's death. He saw Grimm taunting and threatening him. On 24 December, Walter attracted the attention of his neighbours when he threw a snowglobe at his hallucination and it broke a window. The Twelfth Doctor, Devina, and Jess Collins broke into Walter's house and Walter saw them being killed by Grimm's touch. Walter was then taken away in an ambulance so that he could recover from his mental issues. (COMIC: Be Forgot)