Chronomantic Escape + Sphinx of the Second Sun + Quasiduplicate

Chronomantic Escape

Sphinx of the Second Sun

Quasiduplicate

How it works

1. Cast Quasiduplicate by paying 1, creating a token copy of Sphinx of the Second Sun.
2. Cast Chronomantic Escape by paying 4, causing creatures to be unable to attack you until your next turn, and exiling Chronomantic Escape with three time counters on it.
3. At the beginning of your postcombat main phase, Sphinx of the Second Sun and the Sphinx of the Second Sun token each trigger, causing you to get two additional beginning phases after this phase.
4. Move to your first additional beginning phase.
5. At the beginning of your upkeep, Chronomantic Escape triggers, removing a time counter from itself.
6. Repeat from step 4 one additional time.
7. At the beginning of your next upkeep, Chronomantic Escape triggers, removing a time counter from itself and causing you to cast it without paying its mana cost.
8. Resolve Chronomantic Escape, causing creatures to be unable to attack you until your next turn, and exiling Chronomantic Escape with three time counters on it.
9. Repeat from step 3.

By cloning Sphinx of the Second Sun with Quasiduplicate, you double up on its extra beginning phases, effectively accelerating your turn structure so that your upkeeps arrive in rapid succession. This rapid progression of upkeeps rapidly strips away the time counters on Chronomantic Escape. Once the last counter is removed, Chronomantic Escape casts itself for free, locking down combat permanently while sending itself back into exile with fresh time counters to repeat the entire defensive lock indefinitely.