Fathom Mage, Horizon Chimera, and Heliod, Sun-Crowned

Prerequisites

• Fathom Mage on the battlefield
• Horizon Chimera in hand
• Heliod, Sun-Crowned on the battlefield
• available

Steps

1. Cast Horizon Chimera by paying
2. Horizon Chimera enters the battlefield, triggering Fathom Mage
3. Resolve Fathom Mage's trigger, putting a +1/+1 counter on Fathom Mage and drawing a card
4. Horizon Chimera triggers, gaining you 1 life
5. Heliod triggers, putting a +1/+1 counter on Fathom Mage
6. Repeat from step 3

Results

• Near-infinite lifegain
• Near-infinite lifegain triggers
• Infinite card draw
• Infinite draw triggers
• Near-infinite +1/+1 counters on a creature