This took me roughly 120 attempts with Rapier, Base Gold Serpent Ring, 7 Luck and 7 Rusted Gold Coins and however many Rusted Coins, so 307 to 257 item discovery. I'm going to share what I wish I knew at the beginning. First off, and by far most importantly, Mimic positions do NOT reset on using a bonfire. This information is present on the enemy wiki page but is more relevant here. It could have saved a LOT of skeletons from pointlessly pulling themselves together today. Secondly, Mimics "remember" their state prior to being charmed and attacked. If you put it to sleep while it was camouflaged, hitting it will put him back into that state. If he was up and gunning for your ****** when you put him to sleep, he'll wake up all hot and bothered. And lastly, you don't need to wait for the mimic to wake up to use the next charm on him. As soon as you whack him awake, if you throw the charm, he'll immediately fall asleep after the waking up animation completes. This animation is shorter if he was never aggressive towards you. I only learned that it wasn't a guaranteed drop in this playthrough because I got it in the dungeon sewers in my first, ignorant of my dumb luck. Luckily I had missed the one just before smouldering lake on this run. If I knew what I knew now I would aggro the one under the dragon on High Wall, lure it to the nearby bonfire as far from the stairs as possible, charm it, whack it, run away, come back to it once it'd given up the chase, and hope he sat down in the optimal position before I started throwing smoke and slaps at him. Happy hunting and good *****ing luck.