Books like Dungeon Madness

Both Cal and Dale have become stronger, each in spite of the other. The dungeon - Cal - knows exactly how much their strength has increased, and is working hard to become exponentially more powerful. His schemes are becoming more complex, and his dungeon - his body - more deadly. Dale has a nasty surprise waiting for him as he works to thwart the plans of the devious dungeon. You see, he is hearing a voice in his head that tries to distract him in critical moments, and so must fight his mind as he fights deadly creatures. Unbeknownst to both, they are in for the fight of their lives as madness threatens the land...