Both Uses of

medieval
in
The Lords of Discipline

Those found guilty of an honor violation were drummed out of the Corps in a dark ceremony of expatriation that had a remorseless medieval splendor about it.†
Chpt 1.1 *

Tradd and I were studying together for a test in medieval drama, straining irritably to extract meaning from those lean, extinct words that had fallen unmourned from the language.†
Chpt 4.37

Definitions:

(1) (medieval)
relating to or belonging to the Middle Ages

(The period of European history beginning with the fall of the Roman Empire and followed by the Renaissance -- roughly 500-1500 AD)

Often thought of as a time of instability, superstition, plagues, feudal lords, and knighthood.
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Much more rarely, medieval may be used to refer to something as old-fashioned and unenlightened.