The Corel Valley is an area that every player passes through during their playthrough but few recognize as such. This is because the Corel Valley is just two screens that you trek through on your way to the Icicle Inn after you get through Bone Village and the Sleeping Forest.
There isn’t much to do in the Corel Valley, however, you may want to return to this area before you engage in battle with the game’s most difficult optional boss: Ruby Weapon. You can obtain Dazers from an enemy called a Boundfat which will allow you to paralyze Ruby Weapon. Check out the Ruby Weapon side question section for details:
Guide to defeating the hardest encounter in the game. Note: You should attempt the battle against Emerald Weapon first as it is the easier of the two Superboss battles.
You can find details about navigating through the Corel Valley on the Bone Village walkthrough page.
The map below shows the location of the Corel Valley on the World Map: