Pleiades of the Azure Sky

The are a group of Holy Knights of the Kingdom of Liones lead by Denzel Liones, the Assistant Great Holy Knight. They were assigned to guard the borders of the kingdom by the two Great Holy Knights, Dreyfus and Hendrickson.

Post-Infiltration arc
During the award ceremony held in honor of the Seven Deadly Sins' liberation of the kingdom, three of the Pleiades of the Azure Sky, Deathpierce, Dogedo and Waillo, stepped forward in objection. Having been assigned to the borders of the kingdom, they wished to witness the strength of those who saved the kingdom firsthand. Bartra reluctantly agrees to a friendly match between Meliodas and Dogedo.

Meliodas easily dodges Dogedo's attacks and retaliates with his own. Death Pierce concludes that they've seen enough and leaves, revealing that Dogedo's close friend had lost his life during the battle with Hendrickson.

Ravens arc
When Fraudrin of the Ten Commandments arrives at a town near the borders of the Kingdom of Liones, two members of the Pleiades of the Azure Sky, Arden and Deldry, ambush him using their Powers, Vain and Love Drive, to weaken him. Waillo then knocks out the weakened Fraudrin, and the three drag him away while Grayroad watches them unknowingly.

Trivia

 * The Pleiades of the Azure Sky share a number of similarities with the Seven Deadly Sins:
 * As seen in their fights with Fraudrin, the Pleiades emphasizes teamwork and coordination. This is in contrast to the Seven Deadly Sins, whose greatest strength is their lack of teamwork, according to Meliodas.
 * Both groups directly serve royalty of the Kingdom of Liones. The Seven Deadly Sins serve Bartra Liones, King of Liones, while the Pleiades serve Denzel Liones, his brother.
 * In Greek mythology, the Pleiades represent the Seven Sisters, daughters of Pleione and Atlas, who were turned into stars to comfort their father.
 * In Celtic mythology, the Pleiades were associated with mourning and funerals, which may have served as inspiration for Denzel's ability, Judgement, enabling him to bring forth the ghosts of the dead to haunt his enemies.

Seis Estrellas del Cielo Azul