'its mysterious presence filled him with a solemn dread'
'solemn' emphasises the seriousness of Scrooge's situation and how he must follow the ghosts and decide to change. Scrooge is filled with anxiety about what he's going to see as deep down he's aware the actions in his life leading up to this moment all have a negative impact on his future.
this quote also sets up the mysterious and tense buildup towards the realisation at the grave at the end of the stave highlighting exactly what goc yet to come represents