We see a variety of wardens in the book, and most of them have rather mean nicknames. These are men with power, and they often abuse it. But they are also prisoners as well, so most of them are corrupt to some degree, willing to bend the rules if it suits them.
The wardens also play an important role in the book's structure. Shukhov is disturbed and punished unfairly by the mean Tartar first thing in the morning for staying in bed too long. And at the very end of the day, the Snub Nose warder comes to haul poor Buynovsky off to the hole. Shukhov avoided the hole first thing in the morning, but Buynovsky isn't so lucky in the evening.
In a way, the day begins and ends with a warder coming to punish someone from Gang 104. This creates a sort of circular structure to the book and also fits in with one of the book's major themes regarding how the days in the camp are very similar and start running together after awhile. The wardens help to illustrate how the same things just happen ad nauseam (Latin for over and over) in the camp.