The power of the blocking creature and that of Shrill Howler are compared only at the moment that blockers are chosen. Changing either creature's power later won't cause Shrill Howler to become unblocked.
13 Jul 2016
The power of the blocking creature and that of Howling Chorus are compared only at the moment that blockers are chosen. Changing either creature's power later won't cause Howling Chorus to become unblocked.