Instead of fighting against bots/competition on SSG, just keep checking if there is campaign battle in West Sarutabaruta [S]. If there is, join an union then kill the NM Vuu Puqu the Beguiler. That will add the scroll in the union chest in the end.
One of many possible drops from the NM "Abyss Sahagin" in Sea Serpent Grotto located in the area accesible only with the Sahagin Key. Abyss Sahagin has a respawn time of ~16-21 minutes.
Abyss Sahagin drops:
Bard's Testimony
Bastore Sardine
Cobalt Jellyfish
Pamtam Kelp
Scroll of Bewitching Etude
Scroll of Chocobo Mazurka
Scroll of Foe Requiem VI
Scroll of Goddess's Hymnus
Scroll of Herculean Etude
Scroll of Knight's Minne IV
Scroll of Maiden's Virelai
Scroll of Sage Etude
Scroll of Swift Etude
Scroll of Uncanny Etude
Scroll of Valor Minuet IV
Scroll of Victory March
Scroll of Vital Etude
Scroll of Warding Round
Seashell
Shall Shell
