The Phenex Family have inherent powers that are equivalent to that of the legendary creature, the firebird 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 (不死, Fushi), 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 Power. If their energy is depleted by directly attacking their soul using holy objects, their Immortality stops working.
The Phenex Family are also possesses the unique Hell Fire (地獄の火, Jigoku no hi) ability, which can generate and manipulate fire and with its 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 special potion of liquid that can instantly heal injuries.
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 an unknown 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.
|Lord Phenex||The current Head of the Phenex Clan. Father of Ruval, the second son of the Phenex family, Riser and Ravel. He made a arrangement with Zeoticus Gremory for his son Riser to be married to his daughter; the next heiress of the Gremory Clan, Rias Gremory though the arrangement was canceled due to Issei Hyoudou's actions. While he was a bit disappointed by the event, he was pleased that his son learned humility and grew less arrogant.|
|Lady Phenex||She is the wife of the Lord Phenex and the mother of Ruval Phenex, the second son of the Phenex family, Riser Phenex and Ravel Phenex. She traded with Riser to make Ravel a free Bishop so she could be traded to Issei Hyoudou after he became a High-class Devil. She asked Issei to look after Ravel in the Human world and told Ravel to deepen her relationship with Issei. After Issei's promotion to a High-class Devil, she traded Ravel to him as she made preparations for Ravel's future wedding to Issei.|
|Ruval Phenex||The first son of the Phenex Clan and heir to the clan. He is a Rating Game player as one of the Top 10 rankers in the Rating Games and is rumored to be promoted to an Ultimate-Class Devil. During the Azazel Cup, he formed his own team; Team Phoenix, which consisted of members of his peerage and other mythological firebirds as well as immortals.|
|Unnamed Second Son||He has yet to appear in the series, but it is known that he is one of the bosses of a media company in the Underworld.|
|Riser Phenex||The third son of the Phenex Clan and the former fiancé of Rias Gremory. He was scheduled to marry Rias due to their parents agreement as he fought Rias in a Rating Game when she tried to nullify the engagement, winning due to numerical superiority. During the engagement ceremony, he was challenged to a fight by Issei Hyoudou, which he lost. After the loss, he became afraid of Dragons until Issei helped him overcome his fear. He competed in the Azazel Cup, but was eliminated early on due to bad compatibility against his opponents.|
|Ravel Phenex||The only daughter of the Phenex Clan as well as the youngest child of the clan. She was originally her brother Riser's Bishop but was later traded to her mother in order to make her a free Bishop. She fell in love with Issei Hyoudou after seeing his bravery and him defeating her brother Riser. Eventually she moved in with Issei and started attending Kuoh Academy, as she became Issei's manager. After Issei's promotion to a High-class Devil, she was traded by her mother to Issei, becoming his Bishop.|
- 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, with 4 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.