They are always equipped with a Morningstar as well as Throwing Spears, the latter combined with his 500 proficiencies can insta-kill with ease any low tier troop in a single throw. They don a Empire Inlayed Armor and ride an Ironbred Charger.
Agathon Legatus of the Baccus Empire is the only lord that fields Iron Circle Centurions, as they are his household troop. Their stats are greater than those of an un-upgraded Shadow Legion Centurion, having 10 more strength and 4 more agility, but arguably worse equipment.
They are one of the special troops of the empire, the other being the Guardian Empire Knight.
How to Obtain?Edit
Since 3.9, player can obtain them in small numbers. There are 3 known ways to recruit them.
1) By playing a game of chance with Ramun. (You can get 2-4 of them, see this page for details)
In first two options, you also have to pay around 2-5k denars to get the troops.