When Breaching Leviathan enters the battlefield, if you cast it from your hand, tap all nonblue creatures. Those creatures don't untap during their controllers' next untap steps.
11/7/2014 The triggered ability affects all nonblue creatures, including those you control.
11/7/2014 The triggered ability tracks the creatures, but not their controllers. If any of the creatures changes controllers before its original controller’s next untap step has come around, that creature won’t untap during its new controller’s next untap step.