851342 Ninja Army Building Set is a LEGO Ninjago set released in September 2015. It includes Kai and Jay in their Tournament of Elements robes, as well as the Ghost Warriors Howla, Wooo, and various different weapons.
- Originally, the set was known as the "Battle Pack" instead of the "Ninja Army Building Set".
- A very similar set, the 850632 Samurai Accessory Set, was released two years earlier in 2013. That set featured a Stone Scout and a Stone Swordsman, as well as Zane and Jay in their ZX outfits (like the Tournament Robes, these were worn the season before the antagonists of their sets, who were in the next season).
- Howla and Wooo are exclusive to this set.