Rain of Gore applies to all three original cases. It does not apply to combat damage from a creature with lifelink.

Lifelink does not make you gain life. It modifies the consequences of damage. Whatever is dealing damage is causing the life gain.

Rain of Gore is looking for life gain caused by spells or abilities.

- It will apply if a spell with lifelink deals damage, because the spell is causing the life gain.
- It will apply if an activated or triggered ability from a source with lifelink deals damage, because that ability is causing the life gain.
- It will not apply if a creature with lifelink deals combat damage, because combat damage is causing the life gain.

Daniel Kitachewsky
L3, Paris, France
Rules Netrep