Yog-Sothoth

Released in Pump It Up 2015 PRIME, this Nato track takes its name from Yog-Sothoth, an Outer God of the Cthulhu Mythos. The composer later explained on his YouTube channel that the name actually came from a skill in the game Disgaea 4, which he had used endlessly while grinding; it stuck in his memory as suitably grandiose and cool. The BGA is a remake of a general-purpose Prime-era remix animation that had been teased earlier in a trailer. Yog-Sothoth launched an entire themed lineage of follow-ups: a sequel in Prime 2 (2017), Nyarlathotep in XX (2019), and finally Ghroth in PHOENIX (2023).

Yog-Sothoth is defined by its back-loaded design: the closing stretch unleashes relentless runs at 200 BPM. The S23 was Prime's hardest Single chart until Achluoias S24 arrived, opening with staircases before collapsing into a flood of notes. The D25 served as Prime's Double boss song at launch and was reworked in PHOENIX, softening several hold notes. The dreaded D24 awards the Run Lv.10 title for clearing it with an SS rank in XX or an SSS rank in PHOENIX. Even the approachable S9 demands stamina and ends with a rotating pattern reminiscent of Beethoven Virus S7.

A later update (1.01) added an even more brutal D26 to the Quest Zone, subtitled "Minami Raid." A running joke also circulated among players: applying the Rush 110 mod matches Yog-Sothoth's BPM and speed to PARADOXX, the final-boss remix, so people quipped that playing it that way was effectively a "Short Cut version" of Paradoxx. Years later, XX actually added a real Paradoxx Short Cut. The track also crossed over into EZ2AC and Chrono Circle.