Enhancement Stone

That's right, there are a total of 30 Level 8 Sword Enhancement Stones. If you find that last one, it'll be perfect. I wish you wisdom and perseverance until the very end!

Yes, it takes '30 enhancement stones' to make level 9, and if I recall correctly, it was '500,000 gold'.

OMG.. Good luck..! Did you get the 1st floor of the Demon King's Castle (1) or Moon Plains (6)? Or maybe Ghost Hotel (2)?

Oh... Good luck finding that last reinforcement stone..! You can find guides on YouTube (I recommend Yulmae's videos among them, they're well-organized). Have a great day today, and happy Chuseok (even though it's late)!