Could a silver dragon mom fearing the death of her unhatched offspring ever be coerced into giving blood?
Example: A chaotic good, extremely powerful, highly charismatic, and boosted by potions extra wise and smart Bard (and his party) was rudely coerced by the dragon into saving it's eggs. When stealth failed, an entire city of intelligent but evil creatures was destroyed to return the eggs. The reward offered by the ancient dragon isn't useful. The dragon's blood however could to be used to create an "evil" artifact, that the bard intends to use it for good causes. Neither the rudeness nor the potential good cause warrants the dragon's death - but the buffed bard hides the eggs, returns with just one and offers safe return of the remaining eggs in return for a small blood donation.