Warkin was a huge, unkempt male Wookiee who didn't brush his hair and cared little for his appearance. He was easily provoked into Wookiee rage, and only Jedgar was able to keep him from lashing out randomly. Unlike other Wookiee's, Warkin was more than happy to use his claws in combat, an action forbidden to Wookiees who believed such an act was dishonorable and would mark any individual who did so as a "madclaw".
The mad Wookiee willingly served the High Prophet Jedgar and, through him, the dark side itself. He, just like many others, had been seduced and warped by the dark side of the Force and its easy promise of power. As a young Wookiee, Warkin discovered that he had exceptional strength (even among the Wookiee community) which often gave him advantages and power over others. He relished this power, and soon became first the village bully, and then later a dangerous outcast from the entire Wookiee community for using his claws during combat.
When High Prophet Merilli took control of the Wookiee planet Kashyyyk, Warkin immediately went to her to offer his services. Though she arrogantly stated that she needed no bodyguard or assassin to do her work for her, she did recognize the taint of the dark side in the Wookiee's soul. And so Merilli offered Warkin to fellow High Prophet Jedgar as a useful tool and peace offering. Ever since, Warkin served Jedgar faithfully. Though Warkin would generally stay with his master, it was not unknown for Jedgar to send him on missions, as well as for him to go on missions of his own.
Though the mad Wookiee was not Force-sensitive himself, the dark side had "noticed" his actions and offered him even more power. Because of this, Warkin gained the ability to meld with shadows and become invisible, a gift he shared with the Defel race. Warkin was considered a traitor to the Wookiee people, and any Wookiees that he encountered would try to destroy him on sight as a matter of honor. Warkin was an extremely dangerous enemy, and would use every terror tactic he had (such as stalking his prey, leaping out of the shadows to attack then withdrawing, as well setting traps and ambushes) to make his prey fear him before killing them.