Spiders dug themselves a cave on this island... Yuck.
Find the Spider Cave and loot the chest.
Loot and Tips
The cave can be hard to find but it will always have its entrance on the surface and needs a considerably big space underground which is making it impossible to spawn to close to the edge of the island. Try to look for the waving flag next to the entrance. Outside you will face a group of Baby Araktulas and inside two Striped Araktulas will help further little ones. The chest with an Energy Crystal and other items based on the event's level will be in the left corner of the cave. Don't forget to grab the green lantern on the right wall and the Crest of the Spiders outside.
- In case you don't want to face any of the creatures, you can rush to the chest, loot it and reenter the island. All the structures will still be in place but not the foes.