Auspicious Katana was removed from RuneScape after an update, but still exists in-game for those who had obtained it.
An auspicious katana is a weapon that could only be obtained from Treasure Hunter from the very rare slot, purchased with rare item tokens which are only obtainable from Treasure Hunter and were obtainable from redeeming credits in Vic the trader'sstore or during the Blast from the Past Treasure Hunter promotion on 27 February through 3 March 2014. It requires 75 Attack to wield. Its stats are identical to those of the godsword, but the auspicious katana has no passive effect or prayer bonus and weighs less (3.6 kg versus the godswords' 10 kg). It once again became obtainable from large parcels from the Parcels from the Hedge event on 1 May2018 until 30 May2018.
"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.