What does impact of the death mean

"Impact" is an effect.

So "impact" of the death means: the effect that death has on something.

For example, you could say:

The Impact of the death of the Emperor was the loss of respect for the country from the neighboring countries.

or you could say:

The impact of the death of her mother on her was devastating.

Impact is an effect. So, when you say the impact of the death, it means how did the death effect someone. For example, The impact of the death made her sad.