Unknowable Cube

Tap two untapped creatures you control: Put an aspect counter on Unknowable Cube
{t}, Remove an aspect counter from Unknowable Cube: Prevent all combat damage that would be dealt this turn.
When Unknowable Cube has five or more aspect counters on it, transform it.
"I have studied it for years. It reacts to my experiments, but not in ways I could predict."