What is the Twisted Essence of Suffering used for?

Solution 1:

You are correct that it is a horadric cube recipe. It creates a Token of Absolution that allows you to respec. a character.

Added in Patch 1.13, the Token of Absolution is a consumable item that grants the character one stat/skill reset. This works in the same way as the reward from the Den of Evil quest, but allows a character infinite respecs, provided that they are willing to gather the reagents each time they desire a respec. The Token of Absolution is created in the Horadric Cube by cubing together four different Essences that drop infrequently from the act bosses in Hell difficulty.

The Essences include:

• Twisted Essence of Suffering (dropped by Andariel and Duriel)
• Charged Essence of Hatred (dropped by Mephisto)
• Burning Essence of Terror (dropped by Diablo)
• Festering Essence of Destruction (dropped by Baal).

They create: Token of Absolution

source: Diablo 2 Wikia