Like most games in the Castlevania series, Symphony of the Night has different possible endings. To achieve the best ending, one must explore at least 1847 rooms which is normally a huge, time-consuming task.
However, in this run, certain abilities are gained that allow Alucard to move at tremendous speed along glitched routes that players in 1997 could not have even dreamed of.
While traveling through all those rooms, the author, arukAdo, simultaneously acquires all of the relics, making this an "all relics and best ending" run.
Note: Due to an emulation error, the audio in the ending FMV sequence doesn't play.