At the beginning of your upkeep, Extravagant Replication triggers, creating a token copy of Myr Battlesphere.
The Myr Battlesphere token enters the battlefield, creating four 1/1 Myr creature tokens.
Activate Time Sieve by tapping it, sacrificing the Myr Battlesphere token and sacrificing the four Myr tokens, causing you to take an extra turn after this one.