Afflict causes the defending player to lose life; it's not damage or combat damage.

Ammit Eternal's middle ability will resolve before the spell that caused it to trigger. The ability will resolve even if that spell is countered.

Afflict resolves before combat damage is dealt. If this loss of life brings a player to 0 life or less, that player loses the game immediately. A blocking creature with lifelink won't deal combat damage in time to save that player.

If multiple creatures block a creature with afflict, afflict triggers only once.

If a creature is attacking a planeswalker, that planeswalker's controller is the defending player. If a creature is attacking a battle, that battle's protector is the defending player.