gelidas (icy) = the word conveys the hostility of the situation.
superaverat (conquer) = the word conveys his intentions in Rome.
ingentisque (huge) = emphasizes the size of his plans.
parui (small) = calling the Rubicon small contrasts to the 'huge' vision of Rome, it conveys Caesar's disregard for the importance of the river.
trepidantis (anxious) = conveys agitation.
Clara & obscuram ( clear & dark) = two contrasting words together.
maetissima = superlative emphasizes her sorrow
turrigero ( turreted) = vision is turreted as she represents a city. The white hair shows great age - through stress.
lacertis (torn) = appearance is shocking, description conveys she has suffered abuse.
quo (where) = repetition of questions beginning with quo highlights her surprise at them going further. Emphatic position of the word, 'ultra'(further) also shows this.
si (if) = repetition of si shows her disbelief that they can be are law-abiding citizens.
horror (dread) = expresses the characteristic shock and dread at seeing the vision. the violent verb 'struck' emphasizes this.
Caesar's distress is made vivid by its physical nature - his limbs are stuck etc.
languor (weakness) = emphatic position at the beginning of the sentence.