Roseus tree
When Quinn had defeated the Demon tier beast, he had not only received the crystal from the beast but also other rewards alongside it. One of them had been a little seed. Unfortunately, the system hadn't told him what the seed was, or what it could be used for.
Due to the lack of that knowledge, Quinn had been cautious about the seed. His first association had been that it was very likely a seed of the tree itself, hence why he had refrained from planting it where there were plenty of people such as on the Cursed ship.
'Calm down, even if that really is a sapling of that damn tree, that's a good thing, right?' Quinn tried to stay positive, just like the last time. 'Although I'd rather not have to go through such a tough fight again, I have become stronger since then, so I should be able to defeat it. With another Demon tier crystal we'll be able to make another Demon tier item.'