Requires

Morselhoarder must be on the battlefield. Sinking Feeling must be on the battlefield. Multani's Harmony must be on the battlefield. Sinking Feeling and Multani's Harmony attached to Morselhoarder. Morselhoarder does not have summoning sickness. Mana needed:

Steps

1. Activate Morselhoarder by tapping it to add a mana of any color.
2. Activate Sinking Feeling, by paying and putting a -1/-1 counter on Morselhoarder to untap it.
3. Activate Morselhoarder by removing a -1/-1 counter from it to add a mana of any color.
4. Repeat.

Results