I'm curious as to the different techniques players out there have used to kill dragons. Specifically I'm interested in how a high level cleric or mage/sorcerer might be able to battle an ancient red wyrm. The wyrm's massive SR make most spells harmless and an incredible AC makes it impervious to most melee attacks. I know the vulnerablilites like in a very low touch AC attack and a relatively low reflex save but I'm not sure how to exploit that. Any class experiences/stories are welcome.