Use vivid descriptions. Describe the emotions of the tortured character in detail. How they feel when they are being taunted, the physical pain if there is any, and their mental state. Also, describe the setting in a way that enhances the feeling of the torture. For example, if it's in a dark, damp dungeon - like place in the Gacha Life world, it adds to the overall atmosphere of the torture story.
It contributes by expanding the world - view. The 'Made in Abyss' series has a vast and complex world, and 'Old Stories' can show different aspects of it. It can introduce new characters or events that are related to the main story, thus enriching the overall narrative. It might also give a better understanding of the history of the Abyss, which is crucial for a full appreciation of the main series.
The answer is yes. Made in Abyss began as a novel. This original form allowed the creator to lay out the core ideas and storylines that were later brought to life in other visual and narrative formats.
The Made in Abyss manga is on hiatus for now. Maybe the author needs time to flesh out the story or there could be other behind-the-scenes factors affecting the schedule.