This chronological list goes according to the pages in the book Eric, not the order Eric and Rincewind encountered them. The alphabetical list is here.
Death – An anthrpomorphic personification comprised of a skeleton, covered in a black robe, and holding a scythe (or a sword, for kings). He communicates in CAPTIAL LETTERS without the quotation marks.
(Head) Librarian – Formerly human, now simian. Favorite (and nearly only) word: Oook.
Herrena – Full name: Herrena the Henna-Haired Harridan. Check the cover art for full description.
Red Scharron – Friend of Herrena. Known to play canasta.
Diome – Witch of the Night, friend of Herrena. Known to play canasta.
Archchancellor Ezrolith Churn – Tired, old (98, at the time of Eric), hard-of-hearing wizard.
Bursar, The – At UU, but not a wizard.
Senior Tutor – A wizard with unknown duties, except as mentioned in his title.
Rincewind – A seemingly minor wizard who plays a major role in several Discworld novels. He is extremely good at running away.
Luggage, The – A mysterious box made of sapient pearwood that ambles about on hundreds of tiny feet. It arrived in Ankh-Morpork with Twoflower.
Bel-Shamharoth – A many-tentacled monster in whose presence you do not say the number between seven and nine (not 7a). He is also known as the Sender of Eight.
Eric Thursley – Wannabe wizard who manages to summon Rincewind, who thinks he grants Eric 3 wishes.
Astfgl – King of the Demons whose name is infinitely more pronounceable than the demon WxrtHltl-jwlpklz’s.
Duke Vassenego – Demon who missed his chance for glory.
Great A’Tuin – He or she is the turtle who moves through space in the Discworld universe. On his or her back are 4 elephants. On the backs of the elephants rests the Disc itself.
Quezovercoatl – The Feathered Boa, god of mass human sacrifices in the Tezuman Empire.
Tezumen – People of the Tezuman Empire.
Ponce da Quirm – Meets Rincewind and Eric after an unsuccessful search for the Fountain of Youth.
Mazuma – High priest of the Tezuman Empire.
Elenor – A girl in one of Copolymer’s stories. (She had a squint, you know.) Busy mom who was kidnapped from (or by) the Ephebians. A large wooden horse was involved.
Corporal Disuse – Encountered the Luggage during the Tsortean Wars. History is silent as to the outcome, but you can guess.
Lavaeolus – A man in one of Copolymer’s stories – the one with the knee. Also, heroic, Ephebian soldier who may have been an ancestor of Rincewind. His name roughly translates as “Rinser of Winds”.
Private Archeios – As last in the chain of command, Archeios took charge of the child on the potty. (It’s a little complicated.)
King Mausoleum – Kindly (to Elenor, anyway) leader of Tsort during the time of the Tsortean Wars.
Urglefloggah – Demon tagged with a badge that reads “Spawn of the Pit and Loathly Guardian of the Dread Portal: How May I Help You?” (At least his name is pronounceable.)
Azaremoth – Demon, the Stench of Dog Breath. (Have a Nice Day.)
Vizzimuth – Read the Unhealthy and Unsafety regulations governing the Lifting and Moving of Large Objects to the man condemned to push the rock up the hill.
Duke Drazometh – The Putrid. A demon in hell.
Earl Beezlemoth – Three-nosed demon in hell.