Spell Twister

Description
Reflecting the desires of the Soul Sanctum for mastery over SOUL, it improves the bearer's ability to cast spells.

Reduces the SOUL cost of casting spells.

How to Acquire
A secret room on the top of the Soul Sanctum, just before fighting Soul Master.

Usefulness
Since the Shaman Stone has the same price and the soul is generally used for healing, this can be considered a worse version of it (technically it is just "more specific" but not much better on the spell side) in most situations, unless you are using Joni's Blessing or planning to not heal at all.