This game is similar to the CRPGs of old, with all their amazing depth and glaring flaws. There are others that have far more eloquence than I that can make a better argument for that, so I will simply say I enjoyed it.
People keep having trouble with this even though its really easy so i decided to make a guide.
You can wait doing this until after you finished the troll quest but its not necessairy, just slightly faster.
1. Young Hydra (aka the final boss)
Kite him around the tree, you will require a slightly wider arc for him. Try going counter-clockwise. If you are a small character with slower movement speed (e.g. gnome) you will need something to make you go fast here. Size potions, scrolls that give movement speed like haste, anything. CC also helps and makes this guy a fair bit easier to kite.
This is the hardest enemy here due to the regeneration he has (see notes – bottom). Unload everything you have on him (You do have SOME form of damage right?). Bring wands/scrolls if you have no damage of your own whatsoever.
2. Owlbear to the south.
He is much slower and he has fairly poor AC. You can autoattack him to death, even if you only hit on a 20. This WILL take long if you have really poor to-hit and no other form of damage though.
3. The plant to the south near the exit.
Hit her from max distance to aggro her – stay in her sight range so she keeps following you. (There should be a trap near the large door on the floor, stay on the green area – e.g. grass). Proceed to do the same thing as with the owlbear. Note that the Plant has A LOT of range but is extremely slow. Try to stay on the opposite side of the tree.
Casually walk out. Stay on the grass near the large door.
There is a manticore slightly northwest of the tree. He should never aggro on you. If he gives you trouble make sure you do it at night.