Soul Fragment

 is an item dropped from killing the Grim Reaper. It is needed to craft the Soul Whip and Eternal Hoof.

Obtaining
Soul fragments are obtained by killing Grim Reapers, which can be fished during a Spooky Festival, more specifically when the Fear Mongerer is available in the hub. or higher is required to fish up a Grim Reaper.

Trivia

 * The texture for this item is based off of obsidian blocks from Terraria.