mordant

nouns

a substance used to treat leather or other materials before dyeing; aids in dyeing process
mordant
is a type of (narrower)
any material used for its color
"she used a different color for the trim"
color, coloring material, colour, colouring material

adjectives

harshly ironic or sinister
"black humor"; "a grim joke"; "grim laughter"; "fun ranging from slapstick clowning ... to savage mordant wit"
black, grim, mordant
of a substance, especially a strong acid; capable of destroying or eating away by chemical action
caustic, corrosive, erosive, mordant, vitriolic