You need to play in the first difficulty, in the begin area Serenity's Waste





Go out to the lava fall, go into the secret area, to get the "Iwajira" boss





Drop



I get every time 25-30 Moonstone, just check everywhere









If you are lucky, you can drop a orange RPG



After, just come back in the main menu and do it again, you can get the same moonstone drop

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