Equites Clibinarii are a type of heavy cavalry unit available to the Eastern Roman Empire in Rome: Total War: Barbarian Invasion.
They are the heaviest cavalry available to any Roman general. They are intended to batter enemy lines into submission.
If anything the clibinarii wear even more armour than the catafractarii, the other heavy cavalry of the later Roman army. Not only the men but also the horses wear beautifully fitted scale and mail armour that can protect against most melee attacks, and many missile weapons. This type of armoured cavalry force is a late development for the Empire, a practical response to many decades of warfare in the East against assorted Persian dynasties. Having faced such troops, Roman generals could see their worth!
Clibinarii are too slow moving to be used as anything but a massively powerful hammer against an enemy battle line. They are armed for melee, not for the charge. This is not to say they can be thrown into combat without care: any horse will die when skewered upon a spearpoint.