Ezence

Ezence is a pokemon as-of-yet not featured in the Fanon National Dex. It is incredibly powerful, with its stats maxed out. The only way to find it is to use give Arceus Evil Heart, give Giratina Hero's Heart, and leave the two together at a Day Care. Wait a month, and Evil/Hero's Heart will be gone. You will receive an egg. The egg hatches into ??????. ?????? will disappear after a day. Then you need to go to The Gate via Mystery Gift and Ezence will appear to fight you. Use the PokeBalls in this order: Great ball, Master ball, Ultra ball, and DP ball. After you use the DP ball, and Ezence breaks out, use False Swipe. It will delete all of his HP but 1%. Use ten PokeBalls and a Dusk Ball and you'll have him captured. It has appeared in the previous ten Generations, but is not in the Pokedex.

Biological Characteristics
It appears to be a large, black centipede. In the place of its head is the body of Giratina, with the head of Arceus, albeit with its colors inverted.

In the Video Games
The only way to find it is to use give Arceus Evil Heart, give Giratina Hero's Heart, and leave the two together at a Day Care. Wait a month, and Evil/Hero's Heart will be gone. You will receive an egg. The egg hatches into ??????. ?????? will disappear after a day. Then you need to go to The Gate via Mystery Gift and Ezence will appear to fight you. Use the PokeBalls in this order: Great ball, Master ball, Ultra ball, and DP ball. After you use the DP ball, and Ezence breaks out, use False Swipe. It will delete all of his HP but 1%. Use ten PokeBalls and a Dusk Ball and you'll have him captured. It is unknown which game he appears in, as he has only been announced, and not yet encountered by anyone.