This is the continuously active-type Noble Phantasm of Hercules that grants him a "body that knows no death." It is a blessing/curse of the gods, representing immortality, that was granted to him for completing his Twelve Labors in life. It lacks an overt external manifestation such as a weapon or armor, but is the body of the user itself. Because of this, it transforms your body into a tough suit of armor that acts similarly to a conceptual weapon in practice, as a side effect coloring your body like lead.
God Hand has three effects: Resurrection up to 12 times, attack nullification, and "immunity against an attack you have experienced previously."
God Hand applies a conceptual defense, meaning it cannot be worn down. It defends against all attacks of B-rank quality and lower, regardless of the attack being physical or magical in nature. It also grants the effect of automatic regeneration, including resurrection after death, reviving you with a stock of eleven extra lives. You have lives equaling the number of lives, rendering you an "immortal" being who must be killed twelve times to be fully eliminated. For you to be damaged, an attack of A-rank quality or above is needed, meaning that a C-rank attack, no matter how amped up, would still be nullified by God Hand. Even should an attack be capable of destroying the world, since it lacks the Metaphysical Weight needed to get past God Hand.
Unlike Magic Resistance that completely nullifies the attack, God Hand instead allows the attack to take effect without registering any damage. This allows you to attack without even thinking of defense due to it, since they will simply bounce off without leaving a mark.
Multiple lives can be taken at once if the set amount of damage of each life is exceeded from an attack. While any damage can be healed within minutes, the lives lost require a day to heal for each life taken, though this can be sped up by dumping massive amounts of energy into God Hand for faster restocking of lives or healing. Every time you are harmed by an attack, regardless of whether it leads to death or not, you will gain resistance after you heal. In the case of being damaged by flames, you would gain around "+100 fire resistance" after healing. Rather than rendering them "completely ineffective," it makes subsequent attacks almost useless against you. No matter the power of the ability used to kill you, it will be nullified after you resurrect. Even the greatest attack will not be effective on you twice and will require different methods to take each subsequent life.
The one weakness to God Hand due to Heracles' legend is that it is ineffective against Hydra venom. One single strike from a venom-coated dagger is enough to eat through all of God Hand's lives and possibly kill you if you don't set yourself on fire like Hercules once had to.