Both of your commanders are on the battlefield under your control.
Your commanders do not have summoning sickness, and cannot be blocked by your opponents.
({U} magic symbol) ({B} magic symbol) each turn available.
Steps
Declare Silas Renn and your other commander as attackers, attacking the opponent with the highest life total among your opponents and/or an opponent who is tied for the highest life total among your opponents.
Silas Renn and your other commander trigger, creating four Treasure tokens.
Activate Time Sieve by tapping it, sacrificing it and the four Treasures, causing you to take an extra turn after this one.
Deal combat damage with Silas Renn.
Silas Renn triggers, allowing you to cast Time Sieve from your graveyard this turn.
Cast Time Sieve by paying ({U} magic symbol) ({B} magic symbol) .