The Elden Ring Rolling Sparks Ash of War is one you'll want to pick up if you're planning on using one of the new Perfume Bottle weapons in the Shadow of the Erdtree expansion. It causes a chain of explosions in front of you, giving you a far higher damage output than the weapon alone could manage.

This Ash of War is so powerful that it may well be nerfed in a future patch, since it can take out bosses in a few hits, despite the DLC generally being regarded—and even criticised—as being brutally difficult. If you're looking for a build to help you melt those bosses, the Rolling Sparks location is detailed below.

Elden Ring Rolling Sparks location 

It's possible to grab this Ash of War early on in the DLC, but you'll need to take a shortcut to Scadu Altus and venture very close to the Shadow Keep, potentially triggering the Great Rune shattering event. This will progress many NPC quests so it may be best to wait or back up your save file before venturing there.

The Rolling Sparks Ash of War is found on the hill to the south of Shadow Keep and to the east of the soldier camp found there. It's made even harder to spot as it's dropped by a flying scarab you can miss  if you're not looking for it. You can see the exact location where I was standing to shoot it down on the map above. 

Thankfully, you can lock on to the scarab so using a bow, magic, or a throwing dagger will all work, just be sure to finish it off when it hits the ground as it will try to run away. Also, make sure to jump back to avoid the explosion when it dies.

The Rolling Sparks Ash of War can be applied to most Perfume Bottles, and the explosions will take on the element of the bottle: the Lightning Perfume Bottle causes lightning explosions, the Firespark one, causes fire, and so on. Buff it with the Shard of Alexander and Perfumer's Talisman from the main game, and you've got the beginnings of a killer build.