Question: "Imperial" was the second story arc from Grant Morrison's run on the Marvel Comics title New X-Men, running from issues #118-126, it further explored the origin behind the character Cassandra Nova as well as giving more depth to the student body at the Xavier Institute, specifically the Stepford Cuckoos, a set of fictional mutant psychically linked what?

Context paragraphs:
Tattoo (comics): Tattoo, later Longstrike, is a fictional mutant character in the Marvel Comics Universe.  Her first appearance was in New X-Men #126, created by Grant Morrison and Frank Quitely.

New X-Men: New X-Men is a superhero comic book series published by Marvel Comics within the X-Men franchise.  After the end of Grant Morrison's run on titled "New X-Men", the title was used for a new series, "New X-Men: Academy X".  The title was later shortened to simply "New X-Men".

Stepford Cuckoos: The Stepford Cuckoos are a set of fictional mutant psychically linked quintuplets (Celeste Cuckoo, Esme Cuckoo, Irma "Mindee" Cuckoo, Phoebe Cuckoo, and Sophie Cuckoo).  The alphabetical order of the Cuckoos' first names corresponds with their ages, with Celeste being the firstborn and Sophie being the youngest.  Originally calling themselves the Five-in-One, with the deaths of Esme and Sophie the remaining sisters are now known as the Three-in-One.

Here Comes Tomorrow: "Here Comes Tomorrow" is the eighth and final story arc in Grant Morrison's run on the Marvel Comics series "New X-Men", which ran from issues #151-154 (2005).  The storyline featured many controversial elements, such as Cyclops moving forward with his relationship with Emma Frost (prompted by his dead wife), the Stepford Cuckoos being revealed as a development in the Weapon Plus Program, John Sublime being a sentient bacterium bent on bringing evolution to a halt and hints that the Xavier Institute student Ernst and Cassandra Nova are the same person.

New Worlds (comics): "New Worlds" was the third story arc from Grant Morrison's run on the Marvel Comics title New X-Men, running from issues #127-133.  In the aftermath of both the Genoshan genocide and Cassandra Nova's revelation of Charles Xavier's mutant powers, as well as his school's function as a mutant haven, the X-Men must try to broker peace amidst rising human/mutant tensions, while still combating the mutant threats arising worldwide.  This story arc not only dealt with the fallout of Genosha's destruction, but also began the psychic relationship shared by Cyclops and Emma Frost.

Murder at the Mansion: "Murder at the Mansion" was the fifth story arc from Grant Morrison's run on the Marvel Comics title New X-Men, running from issues #139-141.  It features the origin of Emma Frost, revealing her background and back story.

Quentin Quire: Quintavius "Quentin" Quirinius Quire, also known as Kid Omega, is a fictional character appearing in American comic books published by Marvel Comics, usually in those featuring the X-Men.  A green-skinned character resembling Quire appeared in one panel of "New X-Men" #122 (March 2002), and appeared colored pink on the cover of "New X-Men" #126.  Quire appeared in his now-familiar, canonical form in "New X-Men" #134 (January 2003).  He was created by writer Grant Morrison and artist Frank Quitely.

Cassandra Nova: Cassandra Nova is a fictional supervillain appearing in American comic books published by Marvel Comics, most commonly in association with the X-Men.  Created by writer Grant Morrison and artist Frank Quitely, Cassandra first appeared in "New X-Men" #114 (July 2001).  Cassandra is a "mummudrai," a parasitic life form born bodiless on the astral plane.  The mummudrai that became Cassandra became telepathically entangled with the future Charles Xavier, who possesses vast mutant telepathic powers.  This granted Cassandra some psionic powers herself, including the ability to exit the womb and create a body.

E Is for Extinction: "E is for Extinction" was the first story arc from Grant Morrison's run on the Marvel Comics title .  The story was published in "New X-Men" #114–116 in 2001 (formerly titled "X-Men", the series was renamed "New X-Men" at the request of Grant Morrison, but retained its original numbering).  The storyline began Grant Morrison's revamp of the X-Men franchise, introducing a new status quo for the X-Men and the mutant community of the Marvel Universe as a whole.

Imperial (comics): "Imperial" was the second story arc from Grant Morrison's run on the Marvel Comics title New X-Men, running from issues #118-126.  It further explored the origin behind the character Cassandra Nova as well as giving more depth to the student body at the Xavier Institute, specifically the Stepford Cuckoos, Beak, and Angel Salvadore.

Supporting paragraphs: Imperial (comics) Stepford Cuckoos
Answer: quintuplets