Quote from peteroupc »If your opponent casts a spell (including a creature with flash), and it resolves, then players get priority. (For instance, you can now cast Cyclonic Rift at this time.) All this happens during the declare attackers step, so well before blockers are declared.
Quote from cyberium_neo »Thank you. So the moment a blocker is assigned, the attacker is considered blocked, even if I cast CR at this point?