Ectoplasm in The Elder Scrolls IV: Oblivion can be found primarily by defeating Ethereal Undead creatures such as Ghosts, Wraiths, Ancient Ghosts, Faded Wraiths, Gloom Wraiths, Sanctified Dead, and Spectral Sailors. These creatures are most commonly encountered in Undead Dungeons, Necromancer Dungeons, and some Vampire Dungeons, especially after reaching level 6 when there is about a one in three chance that an undead enemy will be ethereal and drop ectoplasm

. Key locations to find Ectoplasm include:

• Rielle Dungeon: Contains 6 ghosts that drop ectoplasm, accessible early in the game and near Bruma. This is one of the easiest and quickest places to farm ectoplasm

• Sancre Tor: Has 26-30 ethereal undead but requires starting the quest Blood of the Divines to enter

• Vahtacen: Contains 7 ethereal undead, accessible after starting the quest Vahtacen's Secret

• Wendir, Malada: Smaller dungeons with ethereal undead

• Undercrofts of Great Chapels in cities: Most cities have chapel undercrofts with 3-5 Sanctified Dead that respawn and drop ectoplasm. Notable chapels include those in Bruma, Leyawiin, Bravil, Anvil, Skingrad, and Cheydinhal. Access may require lockpicking or completing the Pilgrimage quest from Knights of the Nine

Other ways to obtain Ectoplasm:

• Occasionally sold by alchemy vendors starting at level 4, such as "All Things Alchemical" in Skingrad and "The Main Ingredient" in Imperial City Market District. Their stock refreshes every 72 in-game hours but is random

• Loot chests in Necromancer and Vampire dungeons may contain ectoplasm

• A static sample can be found on a table in "All Things Alchemical" in Skingrad

• Previously, ectoplasm was found behind a bench at Meridia's Shrine, but this is no longer present in current versions

Combat tips:

• Ethereal Undead are immune to normal weapons and certain spells like frost and poison. Use silver or enchanted weapons or magical spells to damage them effectively

In summary, the best and most reliable method to farm ectoplasm is by hunting ghosts and wraiths in dungeons like Rielle or the undercrofts of city chapels, using appropriate weapons or magic to defeat them and loot their ectoplasm