Darius made a not bad expression as a response to the Tree Hearts details. It wasn't particularly useful to him nor Gunner and Xela.
Gunner was a half-giant, and his royal blood already made sure he was closer to nature and more in tune with his element than this item. As for Xela, she was an elf using the Life element, so even less of a need to do so.
Darius could either trade it away or bestow it to a trustworthy subordinate. Hm, since he was heading to Elysium, it was better to have some rare stuff on hand in case he met a deity and saw something they had which he liked.
Bartering wasn't a crime, and as long as what he had was good enough, no one could point at him and call him a blasphemer. Even if they did, his preparations ensured that he had the means to deal with any unfavorable situation.