There are 2 pools of dice that always remain on the table: the Spirit Pool and the Dread Pool.
Note: This is only a rough overview - the full rules document explains everything in more detail.

The Spirit Pool represents the strength of the cultists’ connection to their victims, as well as their victims' courage to do what is necessary to survive. All dice within the Spirit Pool act as Spirit Dice.

The Dread Pool represents increasing tension and the likelihood of victims meeting a dark fate. All dice within the Dread Pool act as Dread Dice.

Spirit Dice are resources that can be spent to alter the truths of the scenario in the cultists’ favor or increase their chances of success in a fate roll. 

Dread Dice are what the Shaman rolls against the cultists when fate is tempted. Dread Dice can inflict Sufferings upon victims, such as death.

These 2 pools of dice work in opposition to each other. When a die is added to the Spirit Pool, one is lost from the Dread Pool (and vice versa). The Ritual begins with 7 dice in the Spirit Pool and 1 in the Dread Pool. No dice are ever removed or added to the pools - only moved between them.

DESIGN THINKING
The ebb and flow between the Spirit Pool and the Dread Pool mimics the pattern of tension found in horror movies. As the Ritual progresses, the Dread Pool will grow faster and be harder to contend with. This system achieves a number of additional design goals:

• Even when the cultists ‘win’ a fate roll, they will more than likely lose Spirit Dice as a result (which then become Dread Dice). This means that even victories push the victims one step closer to a dark demise.
  
• By making the ‘health system’ of the Black Box communal, it encourages teamwork, cultist-interaction, and reduces meta-gaming tactics (such as only having the victim with the most ‘health points’ perform actions). Everybody is in danger when the Dread Pool is high.
• It is an intuitive system where the cultists can visibly see the increasing tension of the situation.