Darkhearts hold speechcraft power rivaled only by elementarians and the Four. The minds of the dark mark's bearers quickly shatter. They become paranoid, vain, and cruel, all the while impressing an almost inescapable lure on their swiftly growing mass of followers, which they badly mistreat. Almost all darkhearts had to be brought down violently and usually called a placespirit into existence while dying, which laid further waste to the land.
"We loved our adventurous life. When Astinoi, who had always been gloomy and sensitive, discovered the dark mark on himself, that life shattered like glass. We searched feverishly for help, but when it covered his heart fully, he flung himself down the cliffs into the lake."That darkhearts are both dangerous and rare make them a scarcely researched subject; on the bright side, darkhearts can't be made on purpose, unlike spirit possession. The cause for their coming and probable cures are largely unknown, and they can't be anticipated or avoided. Until the mark covers the entire heart, there's hope; it doesn't grow by any known rules. Voices will help, by sending darkhearts-to-be on dangerous quests, which often claim their lives; but if successful, they die unblemished.
— Tirakanfar, traveller
"Artifacts are hard enough to understand; if made by darkhearts, I wish there was a bottomless pit we could throw them into. Kanmarra's collar alone destroyed half the standing stones in Suyemor in only a day."Artists' notes
— Hinukaya aht Kanamm, whisperer
Darkhearts put a firmly black spot on Genius Loci's bright and hopeful map. But I like the poor fellows somehow; and there aren't as many as the article may make it sound, mind you: only three per generation, in the entire world. Except that they will be known throughout it if they fully bloom.