You become an Immortal Hulk, a being linked to the "One Below All", as such, your powers grow stronger at nighttime and in dark places. This powers grants you various abilities, such as perceiving lies, self-sustenance, communicate with ethereal beings (such as spirits), detect gamma radiation, awareness about if you are being monitored, manipulate your body and even the power to absorb energies, gamma radiation, beings inside you and magic.
The most remarkable feature of this upgrade is that it grants you complete and total control over the "Green Door", which is what grants you, your immortality.
You can't ever be truly killed, because you will always come back.