The knife looks like a black Blood Knife, which is usually undyable.
The name and bonus of this weapon are references to an audio skit made by the Dead Ale Wives, about Dungeons & Dragons. In the skit, one character proudly announces "I've got an Ogre-slaying knife! It's got a plus nine against ogres!" The damage range of the knife (1-4) is intentionally the same damage range as a Dungeons and Dragons dagger (it is expressed as 1d4).
The boss that drops this knife, The Darkness, is a reference to the same skit.