One of the possible new abilities could be resurrection. Just as the phoenix is reborn from its ashes, Naruto might be able to bring himself or others back from the brink of death. This would not only be a game - changer in battles but also have a huge impact on the story. It would add a whole new level of drama and hope to the plot, as Naruto could potentially save his friends or even himself in the most dire situations.
In certain fanfic concepts, Naruto could get the phoenix power during a near - death experience. His strong will to survive and protect his friends could attract the phoenix spirit. The phoenix, known for its rebirth and powerful abilities, might choose Naruto as its host, seeing his indomitable spirit as a worthy vessel for its power.
Well, if Naruto had the power of Achilles, his physical strength would be greatly enhanced. He might be able to move at super - fast speeds like Achilles was known for in combat. His durability could also increase, allowing him to withstand more powerful attacks. Maybe he could even have a sort of 'invincibility' in certain areas like Achilles had his heel as his only weak point.
Another possible new ability is the power of astral projection. Jupiter has a connection to the celestial realm. Naruto, as his son, could project his spirit into the astral plane. This would give him the ability to gather information from afar, spy on enemies, or even communicate with other celestial beings. It would add a whole new dimension to his ninja skills, making him not just a physical fighter but also a spiritual one.
In this fanfiction, Naruto would gain the ability to manipulate the elements in new ways. Each tailed beast is associated with a different element or combination of elements. By having all of them, he could create complex elemental attacks that are not possible before. For instance, he could combine the fire of one tailed beast with the water of another to create steam - based attacks. His healing factor might also be enhanced as some tailed beasts possess regenerative abilities. This would make him even more difficult to defeat in combat.
He would likely gain enhanced cutting and slashing abilities. Each of the seven swords has its own unique properties, so Naruto could use them in combination with his existing ninjutsu. For example, he could use the swords to channel his chakra more effectively, increasing the power of his attacks.
With the Rinnegan, Naruto could also gain the power of the Human Path. This might allow him to read the minds of his opponents or extract information from them in a very unique way. He could also use the Naraka Path to torture his enemies psychologically, which is a very dark but powerful ability that the Rinnegan offers.
Naruto might gain superhuman strength like Kratos. He could easily break through solid rock or lift extremely heavy objects. His speed could also increase, allowing him to move so fast that enemies can barely see him. Maybe he could also have the ability to summon the blades of chaos, which he could use in combat in a unique way, like combining them with his kunai.
Naruto would gain super strength. He could lift extremely heavy objects with ease, like mountains or large buildings in the Naruto world. He would also have super speed, enabling him to move faster than any ninja technique. And of course, he would be able to fly, which is a completely new ability in the Naruto universe.
He could have a 'Solar Sage Mode'. In this form, his body would be surrounded by a bright, sun - like aura. His physical abilities such as strength, speed, and agility would be enhanced to an extreme level. His attacks would also carry the power of the sun, like solar - powered punches or kicks that could cause massive damage.
One challenge could be controlling the new power. Just like Naruto had to learn to control the Nine - Tails' chakra, he'd have to figure out how to use Achilles' power without overexerting himself. Another might be dealing with enemies who would target his new weakness, if he has one like Achilles' heel.