The climax (from the Greek word κλῖμαξ, meaning "staircase" and "ladder") or turning point of a narrative work is its point of highest tension and drama, or it is the time when the action starts during which the solution is given. The climax of a story is a literary element.
so i would say that it contributes by telling us the main action that's about to happen in the story.
The technique that the author uses to build suspense in the excerpt is odd characters are introduced. This is a technique often used in Gothic literature.
