The Dionad-class transport was a type of transport that was produced by Sadon Shipwrights.
History
Dionad-class transports were produced a few years before the start of the Mandalorian Wars and were used by private organizations within the Galactic Republic.
Sadon later developed an updated version of the Dionad-class, the Heraklon-class transport.
Sources
Message to Spacers 9 on Wizards.com (original site is defunct)