The following Object Classes are secondary classes that supplement the object's primary classification.
Thaumiel-class SCPs are anomalies that the Foundation specifically uses to contain other SCPs. Even the mere existence of Thaumiel-class objects is classified at the highest levels of the Foundation, and their locations, functions, and current status are known to few Foundation personnel outside of the O5 Council.
Neutralized SCPs are anomalies that are no longer anomalous, either through having been intentionally or accidentally destroyed or disabled.
Apollyon-class SCPs are anomalies that cannot be contained, are expected to breach containment imminently, or some other similar scenario. Such anomalies are usually associated with world-ending threats or a K-Class Scenario of some kind and require a massive effort from the Foundation to deal with.
Archon-class SCPs are anomalies that could theoretically be contained but are best left uncontained for some reason. Archon SCPs may be a part of consensus reality that is difficult to fully contain or may have adverse effects if put into containment. These SCPs are not uncontainable—the defining feature of the class is that the Foundation chooses to not put the anomaly into containment.