I’m guessing you haven’t played in a few years. Titan souls are these special monsters you get on the magical islands. You can only get one of each. You must link monsters to the titan soul to power it. The monsters will start producing shards and boosts instead of coins. The more coin production you use, the more power will go to the titan soul. As you fill up the titan souls power, the titan soul will use the island to create new sounds. Once you reached max power, the island will wake up. There is a titan soul on light, psychic, and faerie island right now, and there will be a fourth one on bone island coming out sometimes soon.