Activate Bloodbond Vampire using Spike Feeder's second ability by removing a +1/+1 counter from it, causing you to gain 2 life.
Bloodbond Vampire triggers, putting a +1/+1 counter on it.
Repeat.

Infinite lifegain

Infinite lifegain triggers

Agatha's Soul Cauldron

Spike Feeder

Bloodbond Vampire

Activate Bloodbond Vampire by using Walking Ballista's ability by removing a +1/+1 counter from it, dealing 1 damage to any target and causing you to gain 1 life due to its lifelink.
Bloodbond Vampire triggers, putting a +1/+1 counter on it.
Repeat.

Combos with "Bloodbond Vampire"