Rage chest - where is it??? *SPOILER*

[gesaugen]

I've started playing recently, English version, full

On this forum, everyone talks about "Rage chest" which contains spirits of rage, but I can't find it!
I've completed kings first two missions (first with collecting that blue tokens and second with finding his brother) but I haven't got Rage chest in any of those... I've also completed several other quests but none gave me a chest...

So, please tell me exact mission where I should get rage chest and also a picture of inventory where rage chest is would be nice cause maybe I've been missing something on this colorful interface

I'm playing as a warrior. Maybe there's a difference