Agatha's Soul Cauldron + Lurking Roper + Ezzaroot Channeler

Agatha's Soul Cauldron

Lurking Roper

Ezzaroot Channeler

How it works

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

By using Agatha's Soul Cauldron to exile Ezzaroot Channeler, you grant its activated life-gaining ability directly to Lurking Roper, whose inherent static ability skips its normal untap step entirely. Tapping Lurking Roper to gain 2 life triggers its own passive condition, untapping it immediately and creating a closed loop of infinite life and lifegain triggers. This engine also feeds Ezzaroot Channeler's cost-reduction ability (which is likewise accessible through the Cauldron) to make all your subsequent creature spells immensely cheaper to cast.