What the heck is an "event troop"

I have gear that allegedly boosts “event troops” but I don’t know what they are. War season boosts? Useless when they are all towers. War Victor troops? Maybe. Ninjas? 

Clarity would be appreciated. 

Ninjas, Zombies, Yetis. Troops that you win in the ninja event

That’s it? What a waste of a weapon perk. 

Yes, that’s it