Yo doom be inevitable, mon! I am a champion of da Scourge, and no mortal shall stand against me and da mastahs! For Zalazane! For da Lich King!
Me background, huh? It be of no question. What matters be who I am now, mon. And that be somethin' real special, real special, mon.
The Darkspear troll Var'tize was born amongst his people in Stranglethorn Vale. He followed his tribe in all their hardships, watching his mother die at the hands of the Sea Witch's murlocs, and his father by a Kul Tiran cannonball. It was from the corpse of a dead hydromancer that the late-teenage troll picked up a strange charm, the rune-inscribed skull of an orcish necrolyte. He liked the appearance of it, and decided to keep it in a bag of raptor leather, always at his side.
One night, the skull charm suddenly started to glow with an ice-blue light. Intrigued, Var'tize inspected it, and found that the glow acted as a sort of compass. He followed it to one of the island's buildings, where he stumbled upon the (supposed) witch doctor Zalazane, attempting to animate the corpse of a troll who had died just the day before. Even more intrigued, he nevertheless decided to return home. When Zalazane not much later showed his true colors, Var'tize, instead of fleeing with the rest of the tribe, joined the necromancer, and after demonstrating his skill as a warrior by fighting off a large number of undead in a trial of sorts, became his personal bodyguard.
Some years later, strange thing started happening, an invasion of the undead came upon the lands. Zalazane told him that this was the forces of his master the Lich King at work. When yet another, even more powerful invasion force returned about one and a half, two years later, Zalazane gave his champion a quest: he was to seek up the citadel of Acherus, the Ebon Hold, and join training as a death knight of the Scourge. Var'tize immediately accepted, travelled to the Plaguelands, and started his training as a knight. But then came the grand betrayal: the knights of Ebon Hold rebelled against the Lich King. Greatly appaled by this, Var'tize, who had taken the name Zalazthas in honor of his two greatest role models, fled northwards, to rejoin the Lich King's forces.
Nowadays, Zalazthas can be found riding around Northrend on his undead steed Frostecho. To lure unsuspecting adventurers, he may sometimes claim he is a Horde-loyal death knight, but rest assured, he is and forever will be loyal to the Undead Scourge.
This troll be lookin' pretty good for a semi-undead person, mon. A real banshee-magnet, that be for sure.
Another thing to note are the many tattoos inscribed in his skin: an image of Zalazane's voodoo-necromancy mask and one of the Lich King's helmet side by side on his chest, a large image of Frostmourne on his back, an evil-looking skull on the back of his head, runeblades on his forearms, Scourge symbols on both of his hands, and a frost wyrm around each leg.
Zalazthas appears as a dark-skinned Darkspear troll with long white hair and vicious-looking tusks. As a death knight, his eyes glow a pale blue. He prefers clothing and armor that both reflects his status both as a death knight and a (renegade) troll.
Grim and witty? Grim and witty? Someone will die for that, a horrible death. And that be me, from laughter! Ahahahahaa! Nah, just kiddin', it be you who dies.
Zalazthas is, as the above quote illustrates, both grim, and witty. While he takes his duties to the Lich King extremely seriously, he is not the troll to not give a witty comment whenever it suits his kinda random mood. Feel free to joke back to him, but nothing demeaning about the Lich King or Zalanze, then you better already have made funerary preparations.
I don't want anyone to take my skull, mon. Sure, I could survive without my skull, but it just wouldna feel right, if ya know what I mean. How boring it must be to live without a skull.
Zalazthas's most prized possession is his skull charm, which glows with a characteristic ice-blue light (same color as Zalazthas's eyes) that points the owner to where a necromantic spell is being cast or is in effect. It does not point simply to necromancers or undead, they need to cast something. The glow intensifies depending on the power of and proximity to the spell. Other than that, he also possesses a death knight runeblade, death knight armor, and a bag of useful (and less useful) items given to him by Zalazane.