Undertale meets Shield

Nightmare Sans

"Why do you think he'll come to me willingly? If he hid, it was for a good reason. He doesn't just pop up when you say his name three times fast." Sans said. Steve looked at Sans. "Then why did he come when you were dying?" Steve asked, Sans balled his fist before punching the closest thing to him, which was a sofa. A whole went right through the chair as a blaster appeared on his hand. "The same reason he kept me alive when he tested on me. So Papyrus would be his normal self." Sans said, they then heard a noise onto the roof.

"You weren't expecting anyone were you, doctor?" Ink asked, clearly concerned as they all looked at the ceiling. "I was not." Strange said, a giant beam was then shot through the ceiling, almost hitting Sans if it weren't for Ink grabbing him at the last minute. Then Stark, with his iron man suit on and Clint landed down onto the ground with their weapons ready. "Do you all mind not breaking my stuff?" Strange asked, Sans shrugged his shoulders as he stood up. "I thought we weren't supposed to let the little critters out of the cage." Stark said as the mask of his suit came off. "Especially the one were supposed to learn more about."

"You mean by doing tests on me?" Sans yelled as he got up and balled his hands. "Uh, maybe that's a bad idea, Classic." Ink said, Stark looked Ink with confusion. "Looks like we missed one." Clint said and aimed his bow at Ink. "Good thing we got extra room." Clint said and shot his arrow. Everything became slow as the bow was shot. Ink's eyes turned into an exclamation point and another diamond. Sans tried to teleport to get Ink away but he was too tired from glitching out. "NO!" Sans yelled as the bow hit Ink in the chest. Then it started to electric him. Sans then dropped to the ground and began to glitch out again, Strange looked at Sans.

"Don't let the negativity get to you!" Strange yelled, but it was too late. Once all the glitching was gone, Sans was a giant black glob. "What the heck?" Stark said, Sans stood up with his head to the ground. He moved his hand to ink and a black tentacle sprouted out of his back and went to the arrow. It then pulled it out of Ink's chest and broke it. "Strange? Who is this?" Nat asked, Strange made symbols on his hands as Ink looked in horror. "Aw, what wrong Ink?" A demoted voice replacing Sans said. More tentacles appeared out of Sans back. "I thought you need help." He said, Ink scooted back. "N-not from you." Ink said, Stark looked at Ink and then at Strange.

"Sans, I need you t-" Strange said but was cut off when a tentacle went around his neck and lifted him up. "You know my name." He said and slammed Strange down to the ground. "I may be the god of nightmares...." He said and looked up at the ceiling to reveal he had one eye open while the other was covered with goo. "But even I have mercy." He said and looked at the two avengers. "You should choose wisely. It might end badly for you." He said and started glitching out. Once he was done, it revealed a tired Sans.

"I think I know which side I'm loyal to." Clint said and aimed his bow at Sans who was wobbling. Sans fell to his knee but grunted as he got up and looked at the confused and shaken group behind him. "Welp, guess you know part of my dark side. G-gaster has a lab i-in hot lands. Y-you should f-find him-" He stopped and fell to the ground. Ink got up and grabbed his paintbrush. "Uh, bye!" He said and made a portal before jumping in and disappearing. Nat sighed as Thor grabbed Sans and put him on his back.

"You're taking the skeleton back." Stark said, Thor glared at them. "You will not hurt him. He deserves to be free." Thor said and raised his hammer to the two. "Or you will face my hammer." Thor said, a faint yellow glow appeared on his chest. "Fine, but that doesn't mean he shouldn't stay here." Clint said, Strange groaned as he got up. "Agreed, you should have tech to stabilize him. But next time, don't treat that other skeleton like that if you don't want the blood on your hands for all those monsters." Strange said, Stark sighed before nodding. Strange smirked and snapped his fingers transporting all the avenger into a quinjet that was on the roof with Banner inside, typing on a tablet.

"Oh, good. Your back." Banner said and got up and saw the tired Sans. "Just set Sans onto the chair." Banner said, Thor did as he was told and the door was once again closed. He then walked away and Banner kneeled in front of Sans who was strapped in. "What are you doing?" Nat asked when she peeked at the tablet screen. "One of the monsters helped me out in scanning for his health." He said and scanned Sans. The screen then started beeping. "Is that bad?" Steve asked and made his way over as Clint started up the jet.

"No, it says it detects something on his hand." Banner said and looked at Sans gloved hand. "How did we just now notice that?" Stark asked, Banner grabbed Sans hand and took off the gloves to reveal a metal plate screwed into Sans hand. "No wonder this monster hates his father. It does not seem he cared for them at all." Thor said, Banner looked at the font. "W.D.G S1?" Banner read and looked at Sans who sockets scrunched a bit. Banner tried his best to put the glove back on and look at Sans results. "Well, other than that metal tag on his hand, everything seems to be in order." He said and looked at Nat. "When was the last time he glitched?" The trio grew silent.

"A few moments ago. We have to find that black sludge again." Steve said. "What did he turn into?" Banner asked, Thor chuckled and walked over to Banner and patted his back. "Something that will haunt your nightmares." Thor said. "Don't you mean dreams?" Banner asked, cleanly confused. "Nope." Thor said and walked over to sit next to Sans on the other side. The trip was silent as they rode to the helicarrier, awaiting for what came next.