The weapon skill Shockwave is an AoE attack and can cause Sleep. If a large portion of your party are melee-type, consider using Poison Potions. This is not necessary for mages, as long as they keep proper distance. As mentioned, he tends to favor Ground Strike over other attacks.
Zeid also uses two unique abilities; Abyssal Strike, which is a ranged attack that damages and causes a 5-10 second Stun, indicated by a purple flash on Zeid's sword. Abyssal Drain is simply that, a Drain move about as powerful as the spell.
Zeid may have some form of TP Regain, as he will build TP quickly even if being kited and only attacked by magic.
When Zeid is at about 70% HP, there will be a cutscene featuring Volker, who will join you in the fight. You are given time to rest afterwards as Zeid will not immediately aggro again, but Volker will attack if you wait too long.
Volker must be kept alive in order to win and Zeid's Ground Strike can take most, if not all, of his HP in one shot. His attacks hit fairly hard, but he likely won't take hate until your damage-dealing party members are defeated.
At some point, two creatures called Shadow of Rage will spawn. They have attacks equal to Zeid's but much less HP. They are highly resistant or immune to all forms of Sleep. A well-timed -ga spell can kill both in one hit. The Shadows can use Great Sword weapon skills at least up to Shockwave and use the same Abyssal moves as Zeid. They gain TP very quickly, even without being attacked at all.
Zeid will later recall the Shadows if they are defeated, but not immediately. You have 30 to 60 seconds before he does so. Killing them is highly recommended and not very difficult, as they hit nearly as hard as Zeid and can skillchain with him, likely causing the end of your party.
If Zeid is defeated before the shadows, they will despawn.
You won't lose any Experience Points if you are defeated.
An adventurer has been attacked while on an investigation to Xarcabard -- and the attacker is said to be none other than the Dark Knight, Zeid! Report to the President's Office for a briefing on the situation at hand.
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