@jimmywon34 - Thank you for providing this additional information, I've passed it onto the developers now. Idunn's Heart is an unlockable skill in-game, which you unlock from the Bear Tree of the Skill Tree. If you have another look at the skill tree and see it equipped, do let us know! 
@Azhrei21 - Thanks for these specific details about your outfit. Is this the only one that you notice the effect on, or others as well?
@bielik01 - Thank you for sharing the link to this larger thread; I'd encourage the players from this thread to refer to it also. I would however like to issue a quick reminder to be polite and respectful of other players - sometimes it can be difficult to find the right terms to use to find an existing thread, so we do get duplicates from time to time that we merge!
I'll be leaving this thread separate for now, but may merge it later if the issue becomes more widely reported, as to establish a megathread.