At the end of Canto Three of his poem John Shade (the poet in VN’s novel Pale Fire, 1962) mentions ivory unicorns and ebony fauns:
It did not matter who they were. No sound,
No furtive light came from their involute
Abode, but there they were, aloof and mute,
Playing a game of worlds, promoting pawns
To ivory unicorns and ebony fauns;
Kindling a long life here, extinguishing
A short one there; killing a Balkan king;