In the quest, 'this is the pits', you must defeat 12 cursed trees. But on the quest itself, it says to defeat unitnames_00000303. Also, where the cursed trees are in Yagizawa village, there are no names over there heads. They never had names over them in the past even before I had gotten the quest. I think the creatures have no name in general, left out by accident but I just call them cursed trees like how they call them in the quest dialog.