MapleStory/Quests/Exchange Quest

There's a man in Orbis named Staff Sergeant Charlie who is accepting etc drops from specific Ossyria monsters for 500 experience and will give you some rewards.

A list of the tradable items and possible rewards is already compiled on Hidden-Street here.

Some items are more efficient when comparing the gained exp to the exp gained while hunting the monsters. Specifically, the Solid Horns from the Jr. Kitties have the best ratio, as the only other monsters weaker in Ossyria are not accepted in the exchange quest. Other items, like Bain Collars and Lycanthrope Toenails, are merely a novelty exchange, as the reward likely pales in comparison to the items gained while hunting down the monsters.

Some items are also bought in large quantities in use of levelling lower level characters. Though a character levelled by this method needs to be a minimum level 10 to reach Orbis, training is incredibly fast, gaining 500 exp in a matter of seconds. At higher levels, however, this method becomes less efficient. Eventually the exchange becomes merely a way to clear useless etc items for usable items, though selling them for pure meso is always an option. Solid horns are usually preferred to level up a lower-level character, due to the number of players training on the Jr. Kitties at any one time. Zombie Teeth are more expensive, but the chance of getting a Fairy Wing as a reward can offset this extra cost. Also, players train on Zombies far longer than Jr. Kitties. Jr. Yeti Skins fall in between, more expensive from a higher-level monster, and providing better potions than Solid Horns, but nothing too special.

Every exchangable etc item has a specific scroll type (usually 10%) that has a small chance of being given as a reward for a trade-in. However, there are a few exceptions. Solid horns provide Return to Nearest Town scrolls, while Luster Pixie's Sunpieces provide the expensive 60% Cape INT scroll, contributing to the higher-than-average Sunpiece price. Some trade-ins also have special rare items. Notable examples are Ancient Scrolls from Hector Tails, Icicles from Werewolf Toenails (though rarely traded in), and the aforementioned Fairy Wings from Zombie's Lost Teeth.