The Lord Thy God is a Consuming Fire: St. Teresa Margaret Redi of the Sacred Heart of Jesus and the Dark Night of the Spirit

After the great grace of “Deus Caritas Est/God is Love,” the Discalced Carmelite St. Teresa Margaret Redi of the Sacred Heart of Jesus enters a stage of marked passivity in which God is purifying her soul.  This stage is referred to as the Dark Night of the Spirit and falls in the 6^thMansion of the Interior Castle of St. Teresa of Avila.  How does this purification through the dark rays of contemplation occur?  Why is it so painful?  St. John of the Cross uses the analogy of the log of wood and the fire to describe the process of purification of this more interior, darker night.  He also portrays the journey in this Dark Night of Spirit as going up a Secret Mystical Ladder of Love made up of 10 steps.  What are those steps? How do they differ from each other?  How is a soul in this darkest of nights described?  What kind of language does St. Teresa Margaret use to describe her interior sufferings?  What can we learn from all of this?