"The Royal Underground Ensemble - SiIvaGunner: King for Another Day" is a high quality rip of "The Royal Underground Ensemble" from SiIvaGunner: King for Another Day. It represents the King for Another Day Tournament contender Papyrus.
This rip starts off as an orchestral arrangement of "Nyeh Heh Heh!" from Undertale before switching to "Bonetrousle" at 1:01 from the same game. At 3:00 the melody quotes "Don't Forget" from Deltarune.