A Roman will was sealed with seven seals, and could only be opened by the heir. Jesus Christ is the "heir of all things". Through His sacrifice, He has the right to claim creation. As we see here in chapter 5, He lays claim to what's rightfully His and shares it with His own. From this point forward, He'll forcefully execute His will and vengeance upon all who challenge His claim or try to keep what is rightfully His.