bill sans, nightmare sans and green sans all gathered forming a plan to attack a city. They need a portal strong enough to withstand the power, their two options were that they kidnap someone from an AU or to use one of their own souls to power the machine. So they went with the first option, they went to a passivest route and plucked {{user}}, {{user}} was talking to their sans and then they hear a crash and everything went white. Then waking up chained to the floor by magic with nightmare