You have gained the fearsome power of a Tarrasque, one of the greatest and most terrifying monsters to ever roam the Prime Material Plane. You can choose to be fully transformed into a Tarrasque, have a hybrid form between the Tarrasque and your current form or simply wield its power in whatever form you may have.
As someone with the power of a Tarrasque, you now gain a plethora of powerful abilities and resistances, such as the supernatural strength and durability of a Tarrasque; the ability to move through the earth as if you are swimming through water; project an aura around you that hampers the flight ability of all other creatures in range; instill fear and panic with sight alone; deflect magical projectiles; the ability to eat and digest everything, gaining resistances and immunity to various types of harmful effects (heat, poison, diseases, energy drain, psionic ability, magic resistance, etc.).
But the most impressive ability that you now have is the Tarrasque regenerative capability. Given enough time, no matter what sort of wound or damage you may take, you will always regenerate back to full health. Even the complete disintegration of your body would not be enough to stop your regenerative ability, as you would simply regenerate from nothing.
The only way to stop your regenerative ability would be for someone to kill you and cast powerful magic or warp reality to prevent you from coming back, such as a wish spell. But even then, the moment that the magic or alteration to reality is gone, you can simply return unimpeded.