"Auspicious" is a synonym for "lucky", suggesting that this weapon can be indirectly considered a piece of lucky equipment.
There was an increased chance to win the Auspicious Katana on 1 March2014 as part of the "Blast from the Past" Treasure Hunter promotion.
Wielding the katana currently results in an animation glitch. While the weapon is equipped, the player's walking animation uses Legacy Mode animations, even when in EoC mode. As of March 2017, this graphical issue has yet to be corrected.
Killing a player who has this in the Wilderness doesn't leave anything on the ground.
Before an update, you would lose the katana on death in the Wilderness or any other dangerous activity regardless of having Protect Item on.