A synonym for mastery might be:

instinct
involvement
expertise
bossiness

it is the background information on the characters and setting explained at the beginning of the story. the exposition will often have information about events that happened before the story began. the exposition is often the very first part of the plot.

i dont know if your mis-read or whatever but that says 30 points also. its not so very surprising knowing that the words he spoke was english, the aspect of his "language" i'd say is pretty rare and is very unique to pronounce.