Doom's Time Platform, and Time Stretch

Prerequisites

• Doom's Time Platform on the battlefield
• Time Stretch in hand
• available

Steps

1. Cast Time Stretch by paying its mana cost, causing you to take two extra turns after this one
2. Declare any creature as an attacker
3. When you do, Doom's Time Platform triggers, exiling Time Stretch from your graveyard with two time counters on it
4. Move to your first extra turn
5. At the beginning of your upkeep, Time Stretch's suspend ability triggers, removing a time counter from it
6. Move to your second extra turn and repeat step 4 once
7. Time Stretch's suspend ability triggers, causing you to cast it without paying its mana cost
8. Resolve Time Stretch, causing you to take two extra turns after this one
9. Repeat from step 2

Results

• Infinite turns
• Lock