The save is not great. The level is not always taken into account well. Allies are not saved (the items, yes, and abilities too but you have to equip again). I managed to reach the top of the tree on the right and I destroyed the "thing". There is another one on the ground floor, where there are dryads. A third one is at the bottom of the waterfall, very well guarded by wild flowers. Otherwise, I saw flying white creatures, but impossible to attract them. And I set foot in the cave. I think I have what it takes to create a torch.
What a funny game, lol !
Edit : My character is level 8. I crafted two torches for the cave (the time is calculated for one trip to the cave, so bring another torch for the return) and I found the fourth thing to destroy. I could see that the green ring (found on dryads) gains experience with each hit used against dryads. And there is an item hidden behind one of the pillars inside the castle (at the back) which allows you to craft a permanent item (the ability to see the HP/MP of a targeted enemy).
Edit 2 : I think I finished the demo. The easiest way is to gain a few levels (level 6 or 7 minimum) by hitting the monsters and gaining the Green Ring spell on the dryads. Then, go destroy the 4 nodes. The first one on the right when you arrive in the forest. You have to climb to the top of the tree and survive the 3 monster zones (the first zone is the hardest, because the space is quite restricted). Always attack in front of you without ever targeting a monster. If one of them starts to go around you on the side, you have to change places. The second is at the bottom of the waterfall. Use the Green Ring to kill a few opponents (wildflowers) and reach the node from a distance. Long, but safe. The third is in the dryad zone, where there are no opponents, very simple. And the fourth at the back of the cave (requires 2 torches). Then, approach the central tree to make Titania appear. She's not hard to defeat, but she can spawn wildflowers. You learn the spell Tornado and I think there's nothing more to do after that. I didn't manage to hit the white flying enemies. However, thanks to one of Titania's wildflowers' ranged attacks, one of those flying creatures fell to the ground. Unfortunately, I didn't have time to go and hit her.