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Genis' Evil Weapon is located in Altamira, if you go to sleep at the inn you'll have a chance to see Altamira at night! Go to the casino and there should be a bloke there who wasted all his money on gambling (Can't remember the exact location, just talk to everyone!) He'll ask if you want to buy his kendama, which happens to be Genis' Evil Weapon.

Regal's is in Welgaia, the Angel city of Derris Kharlan, in the first section after you leave the prison there should be a building with multiple floors, most rooms are empty but one of the rooms has Regal's Evil Weapon.

Now... Once you have all 8 other Evil Weapons talk to Abyssion in Flanoir, and he'll tell you where to find Raine's Evil Staff... Or he'll hint about it to be more precise. The staff is owned by the old guy in Sylvarant who owns the toll gate mountain pass, after talking to him you'll get the last Evil Weapon!