usurp

(verb) seize and take control without authority and possibly with force; take as one's right or possession. Synonyms: assume, seize, take over, arrogate. Examples: "He assumed to himself the right to fill all positions in the town." "He usurped my rights." "She seized control of the throne after her husband died."

(verb) take the place of. Examples: "Gloom had usurped mirth at the party after the news of the terrorist act broke."