The Blades are group of dragon slayers in The Elder Scrolls series. In The Elder Scrolls V: Skyrim, it is revealed that they have been almost completely depleted by the Admini Dominion, leaving only two members alive: Delphine and Esbern, both of which are in hiding initially at the beginning of the game, but later come out of hiding. They are well known for holding a grudge against the Greybeards.
Delphine is the first member that the Dragonborn meets. She is first seen disguised as an apprentice for the Jarl's Court Wizard in Whiterun, it is later revealed that she had stolen the horn of Jurgen Windcaller, founder of the Greybeards from his tomb just north of Morthal. She leaves the note for the Draognborn, whom she knows will attempt to retrieve it for the Greybeards, telling them to meet her in the tavern in Riverwood and having them ask for renting "the Attic Room". There she will confront the Dragonborn and test to see if they are truly who she thinks they are by slaying a dragon near Kynsgrove.
She will attend the conference up at High Hrothgar if the Dragonborn hasn't finished the Civil War questline.
She will also order the Dragonborn to slay Paarthurnax after learning he once assisted Alduin and is still alive. Although the Dragonborn can choose whether or not to slay or spare him, Delphine will state that Dragonborn is either "with them or against them" if they struggle to make their decision.
The eldest member of the surviving Blades, he is scholar who is familiar with the Dragon Uprising and knows where to locate dragon's lairs. He went into hiding within the Ratways of Riften in order to escape the Thalmor. The Dragonborn locates a journal containing information about his whereabouts in the Thalmor Embassy just outside of Solitude. Delphine sends the Dragonborn to Riften and speak with the leader of the Thieves Guild, Brynjolf who after assisting him with a heist, will tell the Dragonborn that he is located in a deeper part of the Ratways behind the storage area. Delphine also tells the Dragonborn to have Esbern "remember the 30th of Frostfall" as a way to let him know that they were sent by Delphine.
He will attend the conference atop High Hrothgar if the Dragonborn hasn't finished the Civil War Questline.
He will order the Dragonborn to slay Paarthurnax after learning he once assisted Alduin and is still alive, however he will offer his condolences if the Dragonborn wishes not to slay him.
Upon settling down at Sky Haven Temple, Delphine will note that she and Esbern are the only surviving members, and will task the Dragonborn into recruiting new followers. Upon recruiting the first member, the Dragonborn will be able to witness the initiation of the new member. The Dragonborn will be able to recruit up to three members before being given the task to slay a dragon with all the new recruits.