Agatha's Soul Cauldron, Lurking Roper, and Soulmender

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Lurking Roper on the battlefield
• Soulmender in exile
• Lurking Roper has at least one +1/+1 counter on it and does not have summoning sickness

Steps

1. Activate Lurking Roper using Soulmender's ability by tapping it, causing you to gain 1 life
2. Lurking Roper triggers, untapping itself
3. Repeat

Results

• Infinite lifegain
• Infinite lifegain triggers