Maybe it's been documented already but you can spam S3 repeatedly with 1,2, and 3* Hulk on epic Last Stand starting when both hulk and any opponent are unstoppable at the same time and you have S3 ready. I can spam S3 indefinitely till I win the fight, for a good 3 or 4 minutes. With 1* hulk, it takes awhile but infinite S3 mechanic going on there and I can't find any reason for it in my masteries or ability descriptions. Should cost 50% less but it appears to cost 100% less if you tap fast right when the S3 animation ends.