The 'Knife of Tindalos' is a Weird blade that cuts around corners and angles.
"[H]e draws his Tindalosian Knife, the Weird blade that only reflects images that fall on its edge."
It can be used by a skilled practitioner to cut the shadows off living or recently deceased animals (there is no evidence that it can be used for shadows of plants or inanimate objects).
The Knife can be used as a regular weapon to cut through living flesh, with unpredictable but inevitably fatal results.
Unknown. Currently in the possession of Arcturus.
A reference to The Hounds of Tindalos.