There's not much references to gameplay in this chapter.
"Lord of the Flies" mentioned by the teacher may refer to Beelzebub, whose main theme (fly) is shown pretty prominently on creatures that are/supports Crystal Zeniths.
Who are the Crystal Zeniths? They appear to be the main antagonist of this manga. They show up in all civilization but their main gimmick is
colorless.
As a gameplay slang, 'crystal' refers to the cards that were placed on mana zone
face down. You can't do that by charging normally but only through spells and abilities. Once cards are put/turned face down in the mana zone, they were treated as colorless (so you can only tap them to produce colorless mana).
https://duelmasters.fandom.com/wiki/Crystal_Mana