A lot of people seem to be confused as to how this system works. Please allow me to explain.
there are 4 core classes. Mage Rogue Cleric and Warrior
Under these for core classes are 8 unique and independent skill trees. These trees are called souls.
You will be able to select a starting soul, or in essence your first skill tree. As time progresses you will be able to select a 2nd skill tree(soul) and an eventual third skill tree(soul.)
Now as you add points into your skill tree you begin to unlock core skills of the souls. For example if i put 31 points into tree one and 20 points into tree 2 I will have more core skills unlocked in the first tree than the second. You have 51 points to distribute at any given time. You can only have 3 souls at any given time.
However, you can with a game mechanic (Unspecified at this point), change your souls to a different set of 3 of the 8 under your core skill.
Please feel free to post any questions below.