Diablo II/Act III
Alkor is a reclusive alchemist who sells potions and lets you Gamble on his unidentified magic items. He initiates the quest "Lem Esen's Tomb" and plays an important role in the quest "The Golden Bird."
Asheara is the leader of the Iron Wolves, a group of powerful mercenary mages. She can hire off her Iron Wolves for a small fee.
Hratli sells weapons and armor, and can repair your damaged equipment.
 Deckard Cain
Deckard Cain accompanied you to Kurast to give you advice and to identify your magic items.
A member of an ancient order sworn to hunt down corrupt mages, she is in Kurast due to the suspicion that Ormus, a follower of the now extinct old religion of Skatsim, is one such mage. She disappears at the end of the act.
Ormus can heal you and sell you caster weapons, armor and scrolls. He initiates the quests "The Blackened Temple" and "The Guardian."
Meshif can bring you back to Lut Gholein should you wish to return. He plays an important role in the quest "The Golden Bird."