This tool works like a short-ranged flash bang grenade. If enemies are close enough, you can temporarily stun or blind them, allowing you to follow up with a combat art, preferably one that deals high damage to either vitality or posture. This tool is also effective against beasts such as the Blazing Bull boss on the way to Ashina Castle. This tool can be used to a lot of enemies, including bosses and mini-bosses.
You need to purchase Robert’s Firecrackers for 500 sen from either the Battlefield Memorial Mob or Crow’s Nest Memorial Mob merchants.
You’ll access to the prosthetic tool upgrade menu after defeating Gyoubu Oniwa and getting the Mechanical Barrel he drops. Talk to the Sculptor and give him the barrel to unlock the menu.
Similar to skills, there are also upgraded versions of prosthetic tools that will require pre-requisite upgrades before you can unlock them. Each upgrade will require upgrade materials; higher tier upgrades requiring uncommon or rarer materials. Take note that you can still use the older versions of the tools should you wish to.
* Spring-load Firecracker
* Long Spark
* Purple Fume Spark