As a child, I had a book "Petrovich and Patapum", or rather, a whole series of five stories. They were written by Roman Kamushkin (the first parts were co-authored with Alexander F. Sklar, by the way) and stunningly illustrated by Marat Votsayev. Honestly, these books are so good that it feels like they came here from a different reality.
So, in the last, fifth (in my opinion, it was called “Petrovich and Patapum in the Land of Ghosts”), the same Dark Lord on the black unicorn acted.

Two-headed black unicorn