Battlefield 1/Dark Souls Bonfire
On the map Rupture, a bonfire can be found just outside the map boundaries near objective C (in Conquest). Inside the bonfire there is a sword which looks identical to the saber and can 1-hit-kill enemy soldiers. The sword will be lost if the player redeploys and will not respawn in the current round. The sword inside the bonfire is a reference to the game Dark Souls, confirmed by the level designer legmek in this tweet.