Passage: While the two fight, Strange activates Protocol 10, which is revealed to be a scheme to wipe out the entire population of Arkham City and destroy the criminal element of Gotham. TYGER troops begin executing inmates as Strange launches missile strikes on Arkham's denizens from his base in Wonder Tower. A missile hits the steelmill, burying Batman under rubble. Before Joker can take advantage of the situation, Talia arrives and offers him immortality in exchange for sparing Batman's life. After escaping with the help of Catwoman, Batman is convinced by Alfred to end Protocol 10 before pursuing Talia and Joker.Batman infiltrates Wonder Tower and disables Protocol 10. Ra's al Ghul is revealed to be the true mastermind behind Arkham City and mortally wounds Strange for failing to defeat Batman. With his dying breath, Strange activates "Protocol 11", the self-destruction of Wonder Tower. After Ra's commits suicide to avoid capture, Joker contacts Batman, threatening to kill Talia unless Batman meets him at the Monarch Theater. When Batman arrives, Joker demands the cure from Batman but is impaled and apparently killed by Talia while distracted. Talia admits to stealing the cure from Quinn, before she is killed by a second Joker, still stricken with the disease.The healthy Joker that Talia impaled then reanimates into the shapeshifting Clayface, who is revealed to have been masquerading as a healthy Joker all along at the ailing villain's request. Batman defeats Clayface despite Joker blowing up the theater floor. Batman drinks a portion of the antidote, and destroys Ra's' rejuvenating Lazarus Pit before the Joker can use it. As Batman debates curing his foe, Joker attacks him, causing the antidote vial to inadvertently smash. Batman admits that in spite of everything Joker had done, he would have saved him. After Joker finally succumbs to his illness and dies, Batman carries his body out of Arkham City. As Commissioner Gordon asks what happened, Batman places Joker's body on the hood of a police car and leaves in silence.

Question: what did strange activate?
Protocol 11