Nightmare x Reader (You will be mine)

Nightmare when I heard those words from Y/N telling me she was pregnant I was very excited. 9 months later one night I hear Y/N screaming so I knew it was time to get her to the doctors. Nightmare paced back and forth waiting nervously for my baby to be born. Dust said, "Nightmare calm down and sit down she's fine." Nightmare said, "Yes I know but I don't understand why I couldn't go in with her." Horror said, "The doctor doesn't want you to get our gooey stuff on the baby and make them sick." Nightmare said, "I guess you're right." The doctor said, "Alright Y/N just keep pushing I can see the head." With the next big push, Y/N did out came the baby she heard the baby crying. The Doctor said, "OK there's another one in there to keep pushing for it to come out." The baby came out turns out Y/N was having twins which her and Nightmare never knew that. The nurse went out to the waiting room and called Nightmare to come with her. Nightmare got to Y/N resting room and saw her looking very tired that's when the doctor came in. The doctor said, "Congratulations Nightmare you're a father to a healthy baby girl and boy you can go see them now." Nightmare was shocked to find out that Y/N had twins. Y/N said, "What should we name them Nightmare?" Nightmare said, "I think we should name them Lunar and Eclipse." Y/N said, "Those names sound lovely Nightmare dear." The first six months were very hard on Nightmare and Y/N the babies cried constantly. By the time the twins first birthday came Chaos wasn't stone anymore but was very confused and refused to talk to anyone.

Time skip to when the kids are one year old cause I'm lazy

Nightmare was happy that everything was going as planned. Iris explained everything to Chaos Sans he didn't understand much but was happy to be reunited with his longtime friend. Chaos said, "So Iris you and this Nightmare fellow come to where I was turned to stone and brought me here?" Iris said, "Yes he did he knows someone who can help us get back to our AU." Chaos said, "Good I wish I could see mom, dad, and Papyrus again but, I know I can't change anything mom and Papyrus are gone." Iris said, "So why not get revenge on the ones who turned you to stone?" Y/N came walking in with her children. Y/N said, "Iris and Chaos Nightmare would like to see both of you." Iris and Chaos just nodded and with that, they left and went by Nightmare. Iris said, "You called for us Nightmare." Nightmare said, "Yes I did and I've been planning on going back to the AU where Y/N was from and start fighting with the goddesses there again." Chaos said, "When do we leave?" Nightmare said, "In a few days I will send for my other colleges." Nightmare sent a note to all his collages to come to his castle at once."

Time skip

The goddesses feared that the ones who came and got Chaos Sans would be coming back. Nightmare grinned when he saw all of them scared of them. They opened a portal and went into the AU. Nightmare sent his Shadow Papyrus's to stir up trouble so the real fight could begin. Cinnabar was the first one to leap into action and the battle ensued after that. Chaos used his golden apple of Chaos to wreak havoc on the town. Dust used his Gaster blaster to destroy the building. The townspeople run screaming some of them said we need to pray for the guardian of positivity. Nightmare stabbed Indigo with his tentacles she died right then and there. Horror smiled when he killed four people and listening to the small children scream in horror that their parents or siblings were killed. Hikari used her thunder to try to stop them but ended up killing others in the process of her attack. Eventually, everyone was killed end they all left after that Error deleted the AU so now the reader has no home to return to and is forced to stay with Nightmare forever. 

Time skip again

Ink sensed something was wrong he saw that one of his AU's deleted its self.  Ink thought to himself did Error do this he knows he's not supposed to but if it has anything to do with Nightmare then yeah I can see him doing this.  Ink snapped out of his thoughts when Dream said something to him.  Dream said, "Ink I sensed Nightmare's presents from that deleted AU he had something to do with it he's trying to find a way to keep Y/N  with him I just know it and with Cross on his side they're probably going to go to Chaostale and cause trouble there."  Ink said, "No they're going to try using Cross's overwrite ability to try to fixing the mistakes that Chaos made as a child."  Dream said, "What should we do then."  Ink said, "I don't know Dream we must go to his AU and stop them before they do anything rash."  Dream said, "That's a good Idea and I think I know who can help once we get there."  Ink said, "Well thank god you know someone there."  Ink and Dream left for Chaostale to talk to the gods and goddesses there.  They entered through a portal.  Ink and Dream saw two young girls they both saw Dream and came running up to him.  Daphne and Celestia both yelled, "Daddy you came here to see us."  Ink looked confused as to why they called Dream daddy but he didn't question it.  Dream said, "Hi girls my friend and I need to talk to our grandpa about something very urgent."  Celestia said, "Yes daddy fallow us and we'll take you to him."  They both went off and found Apollo.  Apollo said, "Dream it's been years since I last saw you and it's been over a  100 years since I last saw you Ink so what brings you here."  After a lot of long ass talking they understood what might happen.