Synonyms of name-of-the-game

1 Syllable
name, key
2 Syllables
heavy, urgent, basic, vital, needed, crucial
3 Syllables
important, critical, required, cardinal, integral, bottom-line, life-or-death, meaningful
4 Syllables
nitty-gritty, decisive, significant, fundamental, underlined, requisite, necessary, coal-and-ice
5 Syllables
meat-and-potatoes, constitutive, imperative, indispensable, prerequisite