Lord Monochromicorn is the gender-swapped version of Lady Rainicorn created by the original series designer Natasha Allegri and featured in "Fionna and Cake." He is the loyal companion of Prince Gumball and the boyfriend of Cake. He communicates by using his hoof like a telegraph to communicate with Morse Code, rather than by speaking Korean, as Lady Rainicorn does. He stomps his hoof for a dot and scratches the floor like a line for a dash.
He is completely black with a long, gray mane, entirely different from Lady Rainicorn's multicolor scheme. He is more horse-like compared to Lady Rainicorn.