Arachnophobia is the second optional quest. It is acquired by talking to Kollin, who is located south of the Kalm Waypoint. The objective of the quest is to kill 20 spiders. The spiders don't necessarily have to be the Forest Spiders in Guardia Forest. You can also fight spiders in the Downbelow region and the Ancient Forest. The giant spiders in the Ancient Forest spawn 3 more spiders upon death, that also spawn 2 more spiders upon death. One giant spider is therefore worth 10 spiders. Once the 20 spiders are dead, you can return to Kollin, who rewards you with 250 EXP and 150 Gold. Also, you can talk to him again 2 seconds after completing the quest to obtain the quest Ogre Hunt.