This compartment embodies more Light than the fourth compartment. Angels of both mercy and judgment reside here. These Angels are likened to Generals of the Upper Worlds, while the angels in the prior compartments are compared to foot soldiers. This realm is primarily one of Judgment. But if our actions in the physical world warrant it, we can sweeten judgment through the Angels of mercy who dwell here.
The concept of sweetening judgment can be understood this way: A child misbehaves and the parent reacts with great anger. The parent then spanks the child and harshly scolds him. According to Kabbalah, there is no aspect of mercy included in the actions of the parent. The punishment is pure judgment, rooted in the anger of the parent. But the parent could also restrain himself at the moment anger erupts. He could shut down his reactive nature and release all his negative feelings. Yet the parent still realizes, out of love and concern for the child, that a punishment is called for. Therefore with pure love in his heart, and in complete control of his actions, he reprimands the child. This is still judgment, but it is judgment sweetened with mercy.