Board Thread:General Discussion/@comment-15092879-20130810142246/@comment-4830404-20130810154816

You need to try 22 times for a 90% chance of beating it with a 10% chance and 44 times for a 99% chance of beating it with a 10% chance.

.9 = 1 - .9^x; x ~= 21.854

.99 = 1 - .9^x; x ~= 43.7

Just keep trying with dragons that you do not need for your next opponents. Don't use the ones that you will need.