Synonyms for Mastery:

n.

awareness, consciousness, information, lore, sensitivity, understanding, Familiarity. backing, capacity, education, expertness, greatness, leadership, monopoly, oligopoly. dominion, jurisdiction, over, say-so. act (noun)
subordination.
authority (noun)
authority, birthright, charge, clout, command, commission, control, credential, empowerment, enfranchisement, entitlement, faculty, force, influence, kingship, license, mandate, might, mightiness, office, potency, power, powerfulness, precedence, prerogative, prestige, primacy, privilege, puissance, punch, purview, rank, right, seniority, sovereignty, stature, steam, strength, sway, title, Prepotency.
cognition (noun)
command, control.
command (noun)
coordination, direction, discipline, government, grasp, grip, hold, law, management, prowess, reign, rule, will.
command, expertise (noun)
ability, adeptness, adroitness, capacity, cleverness, comprehension, cunning, deftness, dexterity, expertness, finesse, genius, grasp, grip, knack, know-how, knowledge, power, proficiency, prowess, skill, understanding, Familiarity.
control (noun)
command, dominion, power, sovereignty.
cunning (noun)
art, cleverness, craftiness, deviousness, finesse, foxiness, guile, ingeniousness, ingenuity, quickness, sharpness, shrewdness, slickness, slipperiness, sly, smoothness, subtlety, trickiness, wariness, wiliness, wit, Canniness, snakiness.
influence (noun)
bias, importance, motivation, pressure, pull.
intelligence (noun)
acumen, astuteness, cogency, comprehension, erudition, intellect, intelligence, judgment, knowledge, perspicuity, profundity, sagaciousness, sophistication, wisdom.
knowledge (noun)
expertise.
mastery (noun)
command, control, domination, subordination, supremacy.
power (noun)
energy, vigor.
say-so (noun)
say-so.
skill (noun)
ability, acuity, adeptness, adroitness, aptitude, artfulness, capability, competence, craft, cunning, deftness, dexterity, experience, expertise, facility, flair, genius, knack, know-how, proficiency, skill, talent, technique.
supremacy (noun)
domination, predominance, superiority, supremacy.
victory (noun)
achievement, ascendancy, checkmate, conquest, grand slam, knockout, subjection, success, triumph, victory, win, winning, Subdual.

v.

control (verb)
hegemony.

Other synonyms:

capacity, expertness, say-so. jurisdiction, Familiarity. dominion. Other relevant words:
awareness, backing, capacity, consciousness, dominion, education, expertness, greatness, hegemony, information, jurisdiction, leadership, lore, monopoly, oligopoly, over, say-so, sensitivity, subordination, understanding, Familiarity.