If you keep walking toward the west, you will see a grasslands cave near the valley. Gasses seep up through the cave, making spiders huge and causing tremendous harm to the grasslands.
A giant spider rests in the cave. If we can kill the spider, we will decrease the number of spiders in the grasslands. Hope you don't suffer from arachnophobia!
I will give you a trap for spiders. Use it to draw out the big momma (or possibly daddy) spider and kill it!
There are all kinds of strange monsters in the world. Catch them, and you earn tremendous respect.
Kill them, and you're practically royalty!
Killing this spider will be no easy task. You can't mush it with an encyclopedia or blast it with bug spray or clomp it with a shoe. Unless you have a really big shoe.
You might want to consider hiring helpers.