There are currently seven clans (Kor. 가문들) in the Lukedonian hierarchy. However, at one point in the past, there were 13 active clans recognized by the Lord.
It is implied that six of the former clan-leaders betrayed the Lord after the transition of power 500 years ago. As referred in Chapter 190, all of them were close to both the Lord and Rai. Moreover they were the clan leaders who served the previous Lord and later refused to pass away with him.
Another incident ('a trap set by modified humans') which occurred 100 years ago took the lives of the Landegre Clan's successor (and Gejutel K. Landegre's son) as well as the entire Loyard Clan except for the sole survivor Seira J. Loyard.