Courage of the Colossus us undoubtedly the most broken mastery in league history.
Colossus was the dumbest idea that riot ever had for this game. It allows fighters like Riven to dive 1v5 into a team and gain 1000-1200 health shields effectively killing half the team and getting away with the health they jumped in with.
Colossus should be nerfed, it should be removed entirely. This mastery is about 5x as bad as thunderlords decree was when it was released.
I just got out of a game where Hecarim and Riven were both running Colossus, they could dive our entire team while the back line was dealing all the damage and get out with full health.
This is exactly why people say that riot's balance team cant do anything right.
Edit: just used a calculator. 10 initial shield plus 10 per level is 190 shield plus 7% of maximum health.
365 health per enemy champion!!!!! That's 1825 health SHIELD EVERY TIME A CC ABILITY IS USED.
Riots balance team has got to be retarded.