From Official Wiki of the Renaissance Kingdoms

Custody is a pause of a character decided by the administrators.

It is a measure aimed at the player, not the character.

The reasons for this can be:

  • Checking that the player is not using undeclared multi-accounts
  • Waiting for a payment for the purchase of gems by Paypal

On the interface, when you are in custody, this is indicated by the mention "You are in prison" in the box displaying the activity.