Colonel Jake O'Niall is a semi-retired Temple Knight residing in Witchaven. He still works with the Temple Knights and helps the player to investigate Witchaven during The Slug Menace quest. At the end of the quest, he is possessed by a Sea slug and has been ordered to be killed on sight. He later disappears from Witchaven, leaving behind only his chair.
- This character is a reference to Colonel Jack O'Neill from the Stargate TV series.
- After the Slug Menace quest nothing is left of O'Niall except his chair. Previously, the chair still was shown as a yellow dot on the minimap, but this was removed in a hidden update. However, his chair still has a yellow label.
- The colour of his shirt strangely changes after his possession.
- Like most white and Temple Knights, his name is a play on words, in this case "colonial".