Danger posed by an X-Category Anomaly cannot be reliably mitigated or is sufficiently severe that the risk analysis deems mitigation insufficient.
The risk posed by mishandling the Anomaly is life-threatening and may be calamitous in nature.
X-Category Anomalies are either indifferent or hostile to human life.
Very few X-Category Anomalies are utilised by the Foundation due to the risks involved.