I speak to Arec in el nath, after this i back to kerning and talk to darnk lord. Next, find the Door of Dimension located at Monkey Swamp II, i defeat the dark lord and get black charm. but when I 'm going to turn to the dark lord he dont give me the Necklace of Strength. So i drop the black charm to reset the quest, but nothing but nothing happens. HELP ME PLZ, I WANT TO PLAY WHITH MY CHIEF BANDIT (sorry for my bad english, im brazilian)
You don't physically receive a necklace you should be fine continuing the quest. At least I hope so, since you dropped the black charm.
I'm assuming you talked to Dark lord after you killed the clone and then realized you didn't have the necklace. Next step would be talk to the third job instructor.
http://royals.ms/forum/threads/job-advancement-guide.17014/ Read over the third job portion and continue where you left off.
You can either farm them http://library.royals.ms/?page=items&search=Dark Crystal Ore You need 10 ores and then talk to an ore NPC that can make you a dark crystal, either in Ludibrium or El nath. Or you can buy it in FM/ smega for a seller.