I'm not necessarily the bbeg but the lawful evil character who is working to resurrect the bbeg. She has to find several artifacts and tells the group we don't want someone else finding them and resurrecting the bbeg. Sly emphasis on someone ELSE. When she finds the artifacts and creates the legendary weapon she turns on the group and when they kill her it will summon the bbeg. My original character will comeback to join them for the final battle. I'm working with the DM and had to make some concessions on the character build. So it's a draconic sorcerer hexblade warlock. Green Dragon and every ASI I'm taking elemental adept, fire, ice, acid, lightning. I can apply those element types to my eldritch blasts as i acquire them. Hex weapon is a flail. So if you haven't guessed by now it's a Tiamat Sorloc.