Time Sieve + Myr Battlesphere + Planar Bridge + Transplant Theorist

Time Sieve

Myr Battlesphere

Planar Bridge

Transplant Theorist

How it works

1. Activate Planar Bridge by paying 8 and tapping it, causing you to search your library for Myr Battlesphere and put it onto the battlefield.
2. When Myr Battlesphere enters the battlefield, it triggers, creating four 1/1 Myr artifact creature tokens.
3. Activate Time Sieve by tapping it, sacrificing Myr Battlesphere and the four Myr tokens, causing you to take an extra turn after this one.
4. Activate Transplant Theorist by paying 2, putting Myr Battlesphere on the bottom of your library from your graveyard.
5. Repeat each turn.

This intricate setup relies on Planar Bridge as your heavy-duty tutor, pulling Myr Battlesphere straight from your library to flood the board with tokens. While you could technically brute-force the Bridge's high mana cost, Transplant Theorist helps grease the wheels by churning through your deck with its loot ability whenever those artifacts enter, while also recycling the Battlesphere back to your library from the graveyard for {2}. Once everything is in place, Time Sieve steps in to devour the Battlesphere and its four Myr tokens as the ultimate sacrifice, turning that recurring horde of metal into an endless sequence of extra turns.