The Phenex Family have inherent powers that are equivalent to that of the legendary creature, the fire bird Phoenix. As such, their abilities reflect that of the legendary bird, where they can regenerate from almost any injuries immediately and are practically impossible to defeat. It is said that the Phenex Family's tears (known as Phoenix Tears) sell for a high price because of its powerful healing abilities, resulting in the Phenex Family's immense wealth.
The home to the members of the Phenex family is a large castle, greater in size than the Gremory mansion which serves as the place of ruling. The castle's outside layout is comprised of the main building with a tall building in the background, surrounded by multiple towers with flames protruding around and at the top. The front tower has embedded, the phoenix emblem. There are also leafless trees that have tiny flames protruding from the tips. At the entrance is a huge golden statue of a phoenix in the middle of a fountain of fire and at the sides there are poles with small flames coming out on top, and also archway structures similar to an aqueduct that also have flames sprouting at the top.
The interior of the castle has a red color theme blended with matching colors. The entryway has a white, square tile floor with large red tiles to the sides with the phoenix emblem embedded. To the sides of the entryway floor are large gaps with huge flames sprouting out, more poles of fire, and elevated platforms with grass and goblets of fire. Everywhere inside has the clan's signature emblem.
Members of the Phenex Family are well-known for their power of immortality, having superior regenerative abilities that can withstand attacks that would otherwise kill a normal Devil. They can also regenerate any lost limbs and even parts of their faces, making them highly formidable opponents in battle. However, their Regeneration is limited by their level of Demonic Energy. If their energy is depleted by directly attacking their soul using holy objects, their Regeneration stops working.
The Phenex Family are also capable of pyrokinesis, the ability to generate and manipulate fire and their most notable use being able to sprout wings of fire for flight, as well as having power over wind.
Members of the Phenex Family are also the only known source for Phoenix Tears, a liquid that can instantly heal injuries, but not restore blood loss and organ loss. However, they may reattach a severed limb.
In order to create the Phoenix Tears, a Pure-blooded Devil from the Phenex Clan is required. The chosen Devil will then go inside a magic-circle which went through a special ritual. They also prepare a cup which went through a special ritual, and they drop their own tear inside that cup which is filled with water. The water inside the cup which has the tear drop added turns into Phoenix Tears. During that procedure, it is stated that the water won't become "Phoenix Tears" if it isn't a tear shed while having an empty mind, as tears with emotions are "That person's own tears." As such, there won't be any effects if it's tears they shed for themselves or others.
The clan symbol of the Phenex consists of a phoenix encased in a circular shape. Their magic circles also have a unique flair, in which flames erupt from it whenever a Phenex Clan member appears.
Members of the Phenex Clan include Riser Phenex, Ruval Phenex, Ravel Phenex, Lord Phenex, Lady Phenex, and a nameless grandchild (nominated in both the light novel and manga). Their second son has yet to appear in the series, but he is known as one of the bosses of a media company.
- In demonology, Phenex is a Great Marquis of Hell with 20 legions of demons under his command. He teaches all wonderful sciences, is an excellent poet, and is very obedient to the conjuror. He is depicted as a phoenix which sings sweet notes with the voice of a child.
- The Phenex Family has the largest number of Devil offspring which is quite rare among pure-blooded Devils.
- Phoenix Tears instantly lose their power if they get contaminated in any way, even by mixing it with water.
- The mythical bird phoenix is known as "the royal bird" and this would refer to the fact the Phenex family are royalty.