Left Eye of the Falmer

This is the reward from the quest Blindsighted, together with the Right Eye of the Falmer.

However this eye, unlike the Right Eye of the Falmer, cannot be sold to vendor or dropped on floor or be stored in house. This is because this is an item required for an upcoming quest, turning in this item to Delvin Mallory in Riften will grant you a leveled Gold reward (up to 3200).

There is one way to sell the Eye however. After the player sells it to Delvin, it will be on a bookshelf near the Thieves Guild vault in The Ragged Flagon - Cistern. You can take the eye and sell it to the fence in The Ragged Flagon for nearly 1000 septims.

Bugs

 * Sometimes when this item is looted from Mercer Frey's body, the quest to deliver it to Delvin may not activate, and he won't take it. When this occurs, the eye is droppable, storable, or sellable, becoming just like the right eye.
 * Fixes
 * Using the console enter : SetStage TGlarceny 80 to give yourself the quest to return the Left Eye to Delvin, then add the Eye to your inventory with the console ( player.additem 1994f 1). Then return to Delvin Mallory to turn in the quest BEFORE killing Mercer. If you kill Mercer before turning the quest in, the quest simply disappear from the journal as soon as you loot the body.
 * You can escape Irkngthand without taking the Eye, take the rest of your items back to Delvin, sell them, and go back to get the Eye off of Mercer's body.