Never seen him before.... who is that guy ?

Oops not sure why I put the R in his name considering I could see the spelling in the picture.

abob101 he is part of the slavers quest.  Starts at a strong camp where you find very young and old people left after a slaver attack. An old farmer asks you to rescue his granddaughter.  You get the choice to hire or fight Daxus the slaver.  

<QuestChoiceDef>   

    <Description>Violence is the only language they will understand. Put them down.</Description>
    <NextObjectiveID>4</NextObjectiveID>
    <Encounter>
        <Liklihood>100</Liklihood>
        <BattleIdentifier>Slaver</BattleIdentifier>
        <WillRespawn>0</WillRespawn>
        <WanderingRadius>0</WanderingRadius>

        <UnitInstance>
            <UnitType>Champion_Daxus</UnitType>
            <UnitName>Daxus the Slaver</UnitName>
            <Level>7</Level>
        </UnitInstance>

etc...

The problem lies with the fact that the Unit

Champion_Daxus weapon is a champion equipment </AutoCreateEquipment>Axe_Berserkers</AutoCreateEquipment>

So it will not show up when you fight him because he is not declared a champion in the xml (on a particular choice part)

Thus, the correct change to this would be to add

<UnitSubclassType>Champion</UnitSubclassType>

        <UnitInstance>
            <UnitType>Champion_Daxus</UnitType>
            <UnitName>Daxus the Slaver</UnitName>
                <UnitSubclassType>Champion</UnitSubclassType>
            <Level>7</Level>  
        </UnitInstance>

This will fix that particular problem.

I'm having an issue with this quest where the game crashes if you hire Daxus and order him to turn on his old employers, as well.

N/A

In contrast I've been able to have him turn on the slavers and not crash. Something is going behind the scenes.

N/A

I fixed... they no uploaded

Well I updated the fix to work appropriately...

https://dl.dropboxusercontent.com/u/75549875/Fallen%20Enchantress/QuestFixes/Quest_Slavers.zip

and updated to include the more recent error fix.