Zaroff is described as having red lips and pointed teeth.
Although General Zaroff pretends to be civilized and dignified, there are hints that he is more animalistic. One of the best examples is a physical description of the general. Right after Zaroff has finished describing Ivan as a bit of a savage, like “all his race,” he reveals that they are the same race, meaning that he too is savage.
"Is he Russian?"
"He is a Cossack," said the general, and his smile showed red lips and pointed teeth. "So am I."
Notice the description of “red lips” and “pointed teeth.” Both evoke animalistic and savage imagery. They inform the reader that Zaroff is not what he seems, assuming that the reader has any notion that Zaroff might be an aristocrat or gentleman.
Zaroff betrays his sadistic nature when he has no qualms about murdering human beings, and describes Rainsford’s problem with it as quaint.
Laughter shook the general. "How extraordinarily droll you are!" he said. "One does not expect nowadays to find a young man of the educated class, even in America, with such a naive, and, if I may say so, mid-Victorian point of view."
Clearly the general is deranged. He believes that he can determine right from wrong. Yet he behaves with utter decorum most of the time. He has extreme talent in hunting and he operates within the rules he has set. It is just that the entire game he is playing is wrong.
General Zaroff appears to be civilized on the outside, and even follows civilized rules, when in reality he is a demented murderer. He thinks that since he is on his own island far away from others he can make his own rules and no one can intervene. Rainsford gets caught up in the game, and has to figure out if he can hold on to his own principles. In the end, does he sacrifice some of those principles to kill Zaroff?