Here you have a link to the FULL version of the OST called REVIVAL.
It sounds very cool. But I am not so sure if it’s really the Didact who is gonna be revived. The soundtrack rather sounds eerie at some parts (kind of Gravemind-like, you know), then it becomes aggressive and powerful. Whatever is going to be awakened must be evil.
So here’s my theory: Reviving that, let’s call it thing is a last resort by the Master Chief and Cortana. Master Chief can probably open the Cryptum or any stasis device that will initiate the Revival because he is a Reclaimer. But maybe there is a bad price for that action. What do you think it could be?