Man, I always end up forgetting someone when I list them out. There's this whole group of classics students at Hampden College, but really it orbits around Richard Papen. He's our narrator, this scholarship kid from a boring California town who gets drawn into this insular, weirdly beautiful world. The core is the Greek class taught by Julian Morrow, this charismatic and morally ambiguous professor. Then you have the 'inner circle': Henry Winter, the terrifyingly brilliant and cold one; Francis Abernathy, the flamboyant and anxious rich kid; and the twins, Charles and Camilla Macaulay, who are wrapped up in their own intense, almost mythic dynamic.
Bunny Corcoran is the lynchpin, though. He's the one outside the group's usual refined aesthetic—loud, crass, a leech. His interactions with Henry specifically set the whole tragic plot in motion. Outside the circle, characters like Judy Poovey and Cloke Rayburn feel like visitors from the normal college world Richard left behind, which just highlights how far down the rabbit hole he's gone.