Druids' Repository and Aggravated Assault on the battlefield.
You control at least five creatures that can attack this turn.
An opponent is unable to block and kill your creatures.
Steps
Declare five creatures you control as attackers.
Druids' Repository triggers five times, putting five charge counters on it.
Move to your postcombat main phase.
Activate Druids' Repository five times by removing five charge counters from it, adding ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Activate Aggravated Assault by paying ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) , causing you to untap all creatures you control and to get an additional combat and main phase after this one.