Arelative pronoun usually introduces a(n) adjective clause adverb clause noun clause prepositional phrase

A relative pronoun usually introduces an adjective clause that usually starts with prepositions like who, which, that, whose, and whom. An example of this is: The singer who sang had a broken voice. 

Relative pronouns are one of the most commonly used sentence structures in the English language.

So the passage is about the comic mask is ugly