The wording of his skills is awful.
From what I understand, his white grants immunity to all his allies, but not to him, instead he takes less magic damage. But the description is far from clear, maybe not...
Anyway, if his white works like that, he's a totally good hero, especially for war defense.
His green adds some magic damage reduce, meh, can ignore it.
His blue adds some heal during his white, probably good, but won't rely on it.
His purple mirrors moon's orange, and is good.
So he's basically a defender version of moon.
What's probably worse is that he combines mechanics of Plant (granting invulnerability) and Karaoke (channels white skills without damage - don't have to be in the battlefield to start). Both of the heroes are buggy as hell, so we can expect Forgotten to be 4 x times buggy, and no fixes whatsoever in the future...