A Sacrifice

This Act 1 side-quest begins when you discover Isaac in the Cultist's Lair, located in the Foggy Bank area. The entrance to the Lair is a trapdoor inside a house just off the Burrwitch road occupied by cultists.

Background
Isaac was in the process of being sacrificed by some cultists and was too far gone when you reached him. With his last breath, he tells you of a valuable stash he hid away out in the swamp.

Objectives

 * Find Isaac's hidden stash in Wightmire.

Guide
Exit the Cultist's Lair and continue up the Burrwitch road until you reach the Foggy Bank Riftgate. Turn left and follow the edge of the river around until you reach a small area where the tree stump is located.

Finding Isaac's Treasure ends the quest.

Reward
Isaac's Treasure contains the Isaac's Spaulders rare item in addition to other random loot. Isaac himself turns into a pile of bones which can be scavenged.

Note: Isaac's treasure can also be found without talking to him, however the quest will not activate and there will be no xp reward. If you find him afterwards, when he offers to tell you where his stash is you can tell him you have already found it, to which Isaac laments that he should have hidden it better.