do you mean the Lost Sword of El Patron?
i found that and another sword by random loot drop while fighting the assassins near Neban the Silent in Beckett's Quarry on Padres del Fuego. i wasn't looking for the sword in particular, just leveling, and i was there several hours before finding them.
"holloween"... celebrated at the end of October in Pixie Hollow?
happy hunting!
fly sail with you later!
Littlebell