During your time as a Keyblade wielder you will have a dream that takes you to your own 'Station of awakening'. There you will have to pass your own Mark of Master exam. Once passed you will become a true Keyblade Master.
You will be able to enter a mental world like the 'Station of Awakening'. When focusing for a few minutes about a person, situation, place or a problem you are faced with you can enter this mental void with stained glass platforms. Each stained glass representing the object of your focus. You will then hear a an unidentifiable voice that may help you realize something about what you were focusing on, but only just enough to help you out.
All Keyblade Masters share the ability to extract the hearts of themselves or others. This can be in full or only parts of the heart, such as extracting the darkness from someone's heart. They are also able to lock the world away, completely cutting it off from the outside. Another ability is to perform the Keyblade Inheritance Ceremony, a trial in which a person is chosen to inherit the power of the Keyblade. You will also gain Keyblade armor and the ability to turn your Keyblade into a Keyblade Glider.
You gain the Power of Waking much like Sora. Allowing you to awaken Sleeping Worlds and Sleeping Hearts, bringing them back to their original state. This grants you the ability to dive into the heart of a person to reach their Station of Awakening in order to wake them up.
You could give emotions to an eldritch monstrosity or an unfeeling robot, a soulless clone or a full blown AI. With enough time and effort even granting them their own Heart, which is almost synonymous with a ‘soul'. The closer the being is to ‘human’ the less time this will take, with someone who is functionally human may take only a few years, while a eldritch horror may take several centuries of close interaction.