A magic item for Dungeon Crawl Classics.
(Sorry for the lack of colour – I work in B&W)
This magic helmet improves the wearer’s Mighty Deed of Arms die by 1 step (or smite die for paladins, or whatever equivalent you want for other warrior types who use something like the Mighty Deed of Arms).
It also gives the wearer paranoid delusions that his fellow warriors and party members want to control and even attack the wearer. Whenever in a situation where trust is an issue (sharing treasure, scouting ahead, guarding the back, letting someone with a weapon stand behind you, having someone practice their skills anywhere near you, etc), the wearer of the Jade Helm must make a DC9 will save or be certain that these actions will cause immediate and irreconcilable harm, and other actions must be taken in their stead.