In addition to menace, Captain N'ghathrod causes each horror you control to double as mill, causing each horror to cause opponents they damage to mill a number of cards equal to the damage dealt by the Horror at hand
Its a 2-drop, a mana dork, and it can attack and generate mana in the same turn
Its colours are a little more limiting, but this will be an all star in any five colour deck
Something like having a 5 mana scry for 2 on a land would rarely be activated and thus rarely worth it over the basic land unless it had no drawback at which point it would see play everywhere with no reason not to
He is great in ramp decks where he gets Mana Vault, Voltaic Key, Mana Crypt and of course lands and he is great in combo decks where he gets Lions Eye Diamond, Pyrite Spellbomb, Chromatic Star and many of the previously mentioned cards too