Drognan is a Diablo II NPC, and is an ancient and wise Sorcerer from an unknown clan, possibly the Vizjerei. Though he does not cast spells to directly aid the heroes in Act Two, his knowledge and research are helpful for completing several of the quests. He is also a merchant, selling potions along with sorceress and necromancer items such as staffs, scepters, wands, tombs and scrolls.
Reference
Drognan is found in the northeastern corner of Lut Gholein, very near the exit, if the map spawns with the gate to the east.