In the final part of the game, once you regain your flight, there is a new Whale Way Station just north of Yggdrasil, called First Forest Whale Way Station. There is a Sparkly Spot here with a Silkblossom and the Tockle will be right next to it, sitting on a fallen tree.
Head north upon entering this area, to see some NPCs chasing a Slime. Speak to the Slime to learn that it’s actually a human named Eliza, who accidentally turned herself into a monster with a spell and was cursed by some monster. In order to turn herself back into her human self, she needs a Supreme Sage’s Staff, a weapon you can create with the Fun-Size Forge. Of course, if you haven’t found the recipe for this yet, then you will have to hunt it down. The recipe is located in the Sniflheim Whale Way Station, so head there and locate the chest (the recipe is called Sage Advice) behind the door that needs the Ultimate Key.
In order to make the Supreme Sage’s Staff, you need three pieces of Wyrmwood, two Spellbound Boughs, a Sage’s Elixir, and two Thinkessences. The Thinkessences can be bought, and you can easily get a Sage’s Elixir from the Octagonia Casino. The First Forest has two Sparkly Spots that yield a Spellbound Bough, so that is easily done there. There is a tree gathering point at Gallopolis Whale Way Station that yields two pieces of Wyrmwood, plus there’s another spot close to the landing at First Forest Whale Way Station. It doesn’t matter about the quality, so just forge the staff, bring it back to Eliza, and you will automatically use it on her, turning her back into a human. You’ll be done with the quest now and your reward is some Crimsonite.