Tyrant Xilian enters the Undertale Universe

The hooded figure had brought the remaining survivors of which are Mettaton, the six human souls, Sans and Flowey. They all were in a room away from the reality of which they knew, the door that led them towards a pocket dimension outside of time, safe from the monster named Xilian. 

Sans spoke to the hooded figure "So, who are you? you haven't told us anything except that we'll meet someone." The hooded figure remained silent as they then stopped, it spoke in a reverberating tone. "We are here." Its cloak fell on himself as he revealed his appearance. Flowey asked "Who the heck are you? And why do you look like a blob?" 

It was W.D Gaster, the watcher of the undertale universe and the one who had perished in the core incident. "I brought you all here to leave this timeline and enter into another. Do not worry, for he cannot feel you here as we are outside the bounds of time and space." The three were relieved, as they were able to find peace after all they went through. 

Gaster spoke, his wingding shaped hands moving over to sans. "I am sorry, Sans, for I was not able to save everyone." Sans shook his head. "Dont sweat it, you tried your best and I cant blame you." Mettaton cut right in and asked "S-So where are we going? You said we are leaving this..Timeline, I don't get it, what do you mean by timeline?"

Gaster responded "There are infinite timelines in the infinite, ever expanding multiverse, each one with a set path that then leads to another after a new branch is made. Which means, if one timeline went into a genocide route, that timeline will then branch out and create a new timeline. There are simply uncountable amounts of timelines and it is rather complex, so I decided to explain it to you in a simpler way." 

"They will be arriving here shortly." Said Gaster, as a bright light consumed the black void that was Gaster's living quarters. Everybody couldn't help but cover their eyes, as it was too much for them to handle. Flowey spoke "T-The hell!?", Mettaton scolded Flowey "Language!" As the light dimmed down to a bearable amount, they all saw an eight winged figure, his eyes seemingly covered by two pairs of small wings as well.

The being spoke, his voice soothing, calming their souls down and extinguishing whatever stress they had. "Come, for your new life starts here." As they all entered through the gates of light, Gaster couldn't help but stay, as it was his mistake to not warm the others sooner. "I will remain here, for I deserve eternal solitude of not warning the others of the incoming threat..I had the capabilities of doing so, but my body never acted out so I had to remain hidden."

The being spoke, though bluntly. "You are correct, for it is your fault for not acting, knowing that you had the power to do something." The angelic being then walked through the gates of light as it closed behind him, leaving Gaster in his own domain as punishment.

Outside, where XIlian was, in the devastating he and Chashkal had created, someone had been watching them from what looked to be a white void. Their bodies seen as showing 'error' glitches all over, they had a wide smirk across their face as their yellow eyes glew brightly. As they talked to themself, their words constantly stuttered in a glitchy manner as well. "Well, well, well..Look's like another anomaly that I'll need to clean up! This disgusting being has no right of being here! It's like he wasn't made for this place at all!"

A variant of sans, named Error Sans, nicknamed the Multiverses destroyer was ready to take action. He opened up a portal into where Xilian was, his sleeves dangling what looked to be blue, red and black strings. "Hello, ANOMALY! Your death has come straight to you and you'll be welcomed into my puppet collection." Xilian wasn't responding or reacting to Error's arrival, his body looked like it was turned into a statue. He tilted his head, smirking "Ah, preserving your energy so you decided to encase yourself in a protective case? Smart, but not good enough to stop me from reaping your soul out!"

Error!Sans

HP: Interchangeable

ATK: Interchangeable

DEF: Interchangeable

Error extended his string towards Xilians statue state, as they wrapped around him Error's eyes widened. "What..Where is it?! Everybody has one! What the bloody hell is this?!" Error retracted his strings, coming to a realization. "Unless, you are already..A puppet..? But that doesn't make sense, how can one control a puppet without strings?!" 

The sky was consumed by what looked to be a pitch black rift, Error looked up prepared, the sounds of the damned echoed through the planet as a gargantuan hand stretched out, the hand having visible corpses scream out for help. Error smirked and aimed his hand up, forming out Gaster Blasters that had a glitchy appearance to them as well. The fired a solid beam of energy, covered in glitching 'Error' markings. As the beam impacted, it did little to nothing, it merely erased one of the corpses instead. As the corpse was erased, it then came back. 

Error was confused and shocked "The shit? You aren't supposed to come back!" He gritted his teeth, summoning hundreds of blasters and firing them towards the hand. The outcome was the same which left Error annoyed even more, the hand then opened up and pinched Xilian's statue body, lifting it upwards and bringing it into the rift. Error just watched as he felt helpless, he muttered. "Those blasts had the capacity of destroying a whole timeline, yet it just ignored it, what the bloody hell was unleashed into this place.."