All ten of the "Zefra" monsters in the artwork of "Chosen of Zefra".
"Zefra", known as "Sephira" (セフィラ Sefira) in the OCG, is an archetype consisting of Pendulum Monsters making its debut in Crossed Souls. Each of the members also belongs to another archetype that first appeared in the Series 9 Booster Packs (3 of them from Duelist Alliance, while the other 2 from The Secret Forces/Booster SP: Tribe Force), except "Zefraath" and "Zefra Metaltron".
In the face of the god of destruction with its true powers regained, those on the surface could do nothing but await their purgation. With her final, faint sliver of hope, Ptolemaeus released the powers of the 9 Yang Zings she had once materialized to control the Sacred Tree at the "sefiroth" system. That power activated the hidden 11th Zefra of the "sefiroth" system, and re-fused the cores of the 10 Zefra. The 11th Zefra chose Zefracore, who possessed auras of both light and darkness, and completed the fusion with its "Core".
[...]The one who stood to face Tierra, Source of Destruction was the protector of the Naturia Sacred Tree, Zefraath. The scale of their battle shook the entire planet, and lasted for one thousand days and one thousand nights. At the dawn of the 1000th day, the forms of Tierra and Zefraath were nowhere to be seen. The only things left were the charred remains of the Sacred Tree, and two Gem-Knights.
Members of this archetype have shining white angelic styled wings with similar pattern and design on their back. The archetype's symbol is a sphere with six-pointed star-shaped outline with the similar design as combined team symbol of the "Gem-Knight" and "Constellar", resembling some sort of a crown. (The symbol can be clearly visible in "Zefra Divine Strike".) These spheres have the same colors as the spheres present in the "Qli" monsters, as well as the glowing canisters of the "Infernoid" monsters. The colors are based on the Queen Scale of Color, the color correspondences of the Sephiroth ascribed to the second celestial world of Beri'ah.
A "Zefra" Deck is primarily focused on Pendulum Summons, as all the members of the archetype are Pendulum monsters, while gaining advantage with "Oracle of Zefra" and "Chosen of Zefra". "Zefra" Decks are encouraged – through the effects of "Oracle" as well as the effects of the individual members – to incorporate Synchro, Xyz, Fusion and even Ritual Summons into the Deck, enabling an astounding degree of potential variety. This deck even has the ability to summon "Sophia, Goddess of Rebirth", one of the most difficult monsters in the game to summon (This is fitting, as the Zefra are supposedly the chosen warriors of "Sophia"). The variety of cards and the search power can also provide resources for the Summon of "Tierra, Source of Destruction". The natural reusability of Pendulum Monsters fits well into this strategy, and can enable the player to perform multiple kinds of Summons every turn. "Shaddoll" Fusion Monsters especially thrive in "Zefra" Decks, which incorporate all 6 Attributes and provides 2 "Shaddoll" Main Deck monsters on its own.
Each member can also be used in Decks of their secondary archetypes, augmenting their existing strategies with Pendulum Summons. For example, "Zefrasaber, Swordmaster of the Nekroz" can function as a reusable substitute for a Ritual Spell Card when paired with other copies of itself and "Zefraxa, Flame Beast of the Nekroz". In fact, the archetype is designed such that its 10 members form ordered pairs for each of the 5 secondary archetypes ("tellarknight", "Shaddoll", "Ritual Beast", "Nekroz" and "Yang Zing"), with one member having a scale of 7 and the other having a scale of 1. For all of the archetypes mentioned, every single Main Deck monster (with the exception of "Chiwen, Light of the Yang Zing", "Pulao, Wind of the Yang Zing" and "Ritual Beast Tamer Lara") falls within these scales, meaning that any monster that is one of these archetypes (except Special Special Summons) can be Pendulum Summoned using their respective "Zefra" pair.
"Zefraath" can be used as the lynchpin of the strategy, having a Pendulum Effect that changes its own Pendulum Scale while searching a "Zefra" monster in the process, providing resources while also assisting on Pendulum Summons even further. Its Monster Effect enables 2 Pendulum Summons per turn and also Special Summons a "Zefra" from the Deck; this can pave the way to Synchro, Ritual or Xyz Summons of powerful monsters. "Zefra Providence" is a generic search card, but its second effect can be used to protect the Pendulum Spells from being destroyed, and "Zefra War" can destroy an opposing card and can even be activated from the hand.