It reveals why Jekyll looked so sad and would not join the men.
The Forum served as a stage for Roman politicians and philosophers. It was a sort of a square where people gathered to hear these politicians and philosophers speak.
Exclaim. it is used to exclaim
"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.
