From Dragon Eye Atlas

Custodias (plural: Custodiases) is the name of low-level administrative officials in Schap. They typically serve a Steward or Grand Steward.

The role itself is fairly generic and Custodiases can be found in various functions, from handling specific aspects of government down to errant and messenger boys. Typically, a specific Custodias will have a specific function, the same way "public official" can mean many different things in our modern world.

Occasionally, a Custodias will also serve a Justiciar, typically temporarily.