He was fierce rival of Lovis because only one of them could become a Dragon Knight.Lovis proved to be the best so he won the competition.Now he is a ghost bound to the Citadel in Broken Valley and his soul is found in the possesion of Amdusias.To free him and complete the quest Lost Soul you must bring him his soul back or you can smash it on the Blood Altar to complete the quest In Cold Blood, thus releasing the ghosts of his servants.
It is interesting to note that Amdusias loathed his master,Maxos and will be infuriated when the aspiring Dragon Knight found out this silly yet wicked jibe directed towards the failed whelp of a Dragon Knight. The idea of the Dragon Knight suceeding the Maxos Temple trials and his ears constantly besieged by the name of his master he depised to the very end is night intolerable. On the contrary, The Dragon Knight has ample delightfully chances taunting Amdusias, even after his death.
In the fight, it is highly recommended to get in close to deal the most damage (use of the Rush attack skill will help achieve this), and that you are at least level 14, You might be able to take him on lower levels if you have a lot of health potions. From afar he can do an explosive shot which can hit you for a massive 160-220 damage (varying on level, ranged resistance) as well as a regular shot for about 30-50 damage. Close to, he can fear you away from him which will then set you up for another ranged attack, or use a regular melee attack. Get in close with two one-handed swords/axes and he will die very quickly. Another alternative strategy is to send in a creature to distract him while you deal the damage.