Crisis is a concept in C2D10 that describes a person's stability, or rather lack thereof. It's an accumulation of stress, trauma, pain, exhaustion or physical injury. What, exactly, it represents is irrelevant. How it influences a character is relevant.
Mechanics of Crisis
Crisis is inflicted upon a character mainly due to setbacks in tests, contests and conflicts. Setbacks cause a character to accrue either strain or stress, leading to a test at the end of the scene to resist the pressure the character is under. Failing to pass that test leads to the character suffering one point of Crisis.
That means that in a single scene, a character can suffer at most two points of Crisis due to these tests. However, there are more ways for the dice to be mean to a character. Or, as is often the case, the Keeper.
At the Keeper's discretion, if the situation calls for it, she may spend 4 villain points to inflict a Crisis on a character that has suffered a setback in a serious enough situation. The player can choose to ignore it, but will then reward the Keeper 5 villian points. A net gain of +1 point for the Keeper, so make a good decision.
If something goes truly pear shaped, a character may suffer more than 5 points of strain or stress in a single scene. If that happens, the excess points are instead converted directly into Crisis. This is called Overstrain, or Overstress, if you prefer to be precise about the cause.
If a character has 4 strain and would suffer two more points, it would leave them at 6 strain, which is not allowed by the rules. This would instead leave the character with 5 strain and convert the extra point of strain into a point of Crisis instead.
At the end of the scene, the character would still have take the strain test to avoid getting yet another point of Crisis. The situation would be the same for stress. Any excess stress would be converted to Crisis if stress would exceed 5.
Overstraining has another big drawback.
Another big drawback of overstraining is that a character instantly must resist defeat or be defeated in a conflict. This is called a breakdown. The stress, or strain, is too much for the character and they must summon all their power to be able stay on their feet, avoiding to either give up to exhaustion, pain or stress.
In difference from resisting defeat from a conflict as a direct result of, this form of resisting can be done as many times as necessary, whereas one can only resist defeat by an active action from an opponent once in a conflict. Granted, each resist costs you another point of crisis. Which leads us to Afflicition.
If a character is at 10 crisis and suffers another point of crisis, it's largely over for them. Suffering that amount of stress, strain, pain and trauma is more than anyone can handle. If a character is at maximum crisis and would suffer another point, they instantly perish in a way appropriate for the conflict or test they are in.
Be it bleeding out, dying to trauma, overloading their stress systems to the point of suffering a heart-attack or permanent mental trauma, they are for all intents and purposes no longer fit to function in any capacity. In most cases, they are simply dead.
Suffering Crisis is a lot easier than getting rid of it. Physical trauma, exhaustion and injuries require time to rest, to do physical therapy, sometimes medical care and medication. Mental trauma, stress and anxiety may require therapy, medication and also rest.
Healing Crisis is a largely narrative process where actions taken by the character is influenced by the method they suffered the Crisis in the first place. If it's mostly mental trauma, then psychotherapy, rest and social support is required. If it's mostly physical trauma then medical care, physical therapy and rest is required.
Striving for recovery
Crisis is very much permanent unless a character truly devotes their time and resources to get rid of it. Any session where a player has acted in a way that the Keeper determines is conducive to their recovery, either by seeking medical help, attending therapy or using any methods of resting and recovering, will heal one point of Crisis at the end of the session.
If a player has also acted in accordance with their ambition and made informed roleplaying choices to advance their ambition may also heal one point of Crisis at the end of the session. Recovering and striving for ambition must not be in conflict for both points to apply.
A faster, temporary way of dealing with crisis is through certain medical substances. Drug abuse is rife in this day and age. Most of the working population use some form of stimulant to even get through the average work day.
A character may acquire and use certain kinds of stimulants to temporarily reduce, or even remove their crisis. This doesn't actually heal any crisis. It only removes the crisis dice for as long as the drug is effective.
Physical therapy requires passing a DC2 Wealth test.
Psychotherapy requires passing a DC4 Wealth test.