Glow Dust in The Elder Scrolls IV: Oblivion can be obtained primarily in two ways: 1. Defeating Will-o-the-Wisps

• Will-o-the-Wisps are ghostly enemies that drop Glow Dust upon death with a near 100% chance.
• They commonly spawn in monster dungeons, swampy or forested areas near water such as south of the Imperial City along the Niben River, near Leyawiin’s Blackwood region, and around Azura’s Shrine northeast of Cheydinhal.
• Will-o-the-Wisps require enchanted, silver, or Daedric weapons, or shock/fire spells to be damaged effectively, as normal weapons do not harm them.
• They tend to spawn more frequently at level 10 and above.
• Examples of good locations include Grey Rock Cave and areas near Oblivion Gates like those near Bruma

2. Buying from Alchemy Vendors

• Several alchemy shops in the Imperial City Market District regularly stock Glow Dust.
• Notable vendors include Claudette Perrick at The Gilded Carafe, Ogier Georick at The Main Ingredient, and Calindil at Mystic Emporium (requires Mercantile skill 50+ to buy).
• Glow Dust can be purchased for around 78 gold and shops restock their inventory every 48 to 73 hours, allowing repeated purchases.
• This method is the easiest and fastest way to acquire Glow Dust without combat, especially useful for quest progression like Azura’s Daedric quest "Blood of the Daedra"

Additional Tips:

• One guaranteed Glow Dust sample can be found in the Bruma Mages Guild Living Quarters but is only available before starting the "A Plot Revealed" quest.
• Glow Dust is essential for alchemy recipes, particularly for potions with effects like Restore Speed, Light, Reflect Spell, and Damage Health

In summary, you can get Glow Dust by killing Will-o-the-Wisps in specific locations or by purchasing it from alchemy shops in the Imperial City Market District, with the latter being the most convenient method for quick acquisition.