"I've always been handy with a blade"
In reality these knights are men who are usually fused to their armour, as their wounds heal often the skin heals around shards of armour and their lesions form over the metal. These men have learned to cope with tremendous amounts of pain in their fanatic states. Their armour is often rusted with gaps that the knights use to self inflict further wounds and allow their diseases to fester.
These knights were part of the Cult of Ryle the Unclean, and were sworn to him.
Whilst the party were under the effects of Garridan’s hallucinogen these knights appeared as wearing candy armour and as such were referred to as lollipop knights.