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Voiced by: Hikaru Midorikawa (Japanese), Daniel Cronin (English; up to episode 10), Crispin Freeman (English; episode 18 onwards and in the Slayers Premium movie) *
From a young age, Zelgadis was apprenticed to his great-grandfather Rezo, eagerly assisting the Red Priest in pursuit of his many goals with a young man's zeal to aid a relative he idolized. Zel asked Rezo for power, in order to help seek out the Philosopher's Stone, and Rezo gave him power, alright: he transformed Zelgadiss into a chimera, sorcerously fusing him with a stone golem and a low-level monster called a brau demon to become a mystically powerful, hyper-strong stone-skinned monster. Zel performed a Heel Face Turn and has been trying to restore his human body ever since. He has the least interest in Lina's little group (to the point he eventually wandered away and was never seen again in the original novels), and usually tends to accidentally cross paths with them whilst searching for cures, often needing to be bribed into tagging along by appealing to his desire to be rendered human again.
Adaptation Dye Job: In the novels and the Slayers Premium movie (which takes after the novels' character designs), Zelgadis' skin is a bluish-green color; in the anime, it is periwinkle blue.
Anti-Hero: Type IV. He doesn't really care about anything other than curing himself (and says so), and will do criminal things like raiding libraries and busting into tombs in search of magical lore, but he can do the heroic thing if properly motivated.
Berserk Mode: Only in the novels; he wasn't just serving Rezo there, but he was also his berserker. Rezo would make him do gruesome tasks by his own hand, and in the novels, Zelgadis clearly regrets doing them. He is this briefly in the anime, but not to the same extent that he was in the novels.
Byronic Hero: Zelgadis's potential for heroism clashes with his melancholic nature and tendency towards self-absorbtion.
Conveniently an Orphan: Word Of God put out that both of his parents are dead. Rezo murdered them out of fear because they were growing suspicious of his experiments, and they were concerned about Rezo's designs for their son.
Cursed with Awesome: The curse placed on Zel has given him Super Strength, Super Speed (seen in the first series), Nigh Invulnerability and enhanced magical ability, but it's also made him a hideous freak. He wants desperately To Become Human.
In Evolution-R, it's revealed that he could have lived with it, if he hadn't discovered that he was being used as a guinea pig in Rezo's quest to cure his sight.
Cute Monster Guy: Zelgadis doesn't look human, and thinks of himself as a monster (and being a magical hybrid of creatures means he's technically right), but he's not unattractive and, arguably, his "monstrous features" are actually part of his charm.
Celibate Hero: Discussed briefly a few times in the novels and in some interviews. In the novels, he mentions once the painful things that would happen to a woman if he got intimate with her, and Kanzaka himself mentions this in interviews, thusly justifying it on a physical level.
Deadpan Snarker: He's the most sarcastic, flat-toned character in the series.
Mr. Fanservice: Despite having green-grey skin studded with stones, he's rather handsome.
First Name Basis: Word Of God has stated Zelgadis' last name (Graywords) in interviews, and the only time it's ever mentioned in canon is by Filia in episode 1 of Slayers TRY.
Flanderization
His reason to cure himself was flanderized, oddly. In the novels, it is for atonement; in the anime, it's mostly because of how he looks - and at times, he takes joy in people's insults every now and then.* Other adaptations don't really address his reason to find a cure, weirdly enough.
Flying Brick: He's supernaturally strong, Nigh Invulnerable (it takes a headshot from a cannon to merely knock him out), and he flies. Through the use of magic for that last aspect, admittedly.
Good Is Not Nice: Equally as nasty as Lina, but in different ways.
Grumpy Bear
Icy Blue Eyes
Purple Eyes: In the novels
I Just Want to Be Normal: Does not like having a rock hard body (pun intended) and constantly searches for a cure.
Incest Is Relative: For a while, it was thought Rezo might be both Zelgadis's grandfather and great-grandfather. This turned out to be a translation error.
Insult Backfire: He's been called a "Heartless Sorcerer/Mystic Swordsman". He likes the sound of it..
Jerk with a Heart of Gold/Jerkass: It varies.
Knight in Sour Armor: Flirts with this. He's far more cynical than the setting warrants, but is at heart a pretty decent guy.
Made of Iron: Well, stone. It is occasionally noted by Lina that the stone skin he hates so much has saved his life many times.
Magic Knight: Balances swordplay and magic well.
Put on a Bus: Along with Amelia after the first arc of novels. Notable because he and she are major characters in all other media, whereas their replacements were mostly novel-exclusive. He also doesn't appear in the Knight of the Aqualord manga.
Raised by Dudes: Implied, given that Rezo was the one who raised him after he murdered his parents, and his most steadfast companions before meeting Lina were a fish man, a werewolf, and two older men.
Red Mage: His strongsuit is Shamanistic Magic, he can perform some Black Magic and knows the basic healing spell in White Magic, and is a decent swordsman, albeit not to the same extent that Gourry is.
Red Oni, Blue Oni: The blue to Lina's red.
Ship Tease: With Amelia.
The Spock: Tends to be the most rational one when it comes to planning, albeit not always.
Straight Man and The Comically Serious: So, naturally, he gets the most humiliation heaped on him. (Zelga-bunny!)
Teen Genius
Unusually Uninteresting Sight: Moreso in the anime than the novels; his appearance doesn't warrant as many reactions as the viewer would expect, given what he's established about it. The one notable time it actually is is during a flashback. It also makes less sense because he gets negative reactions in the novels, and there are far more chimeras that appear there.
Word Of God: Like Gourry, many things about him are stated in Kanzaka's interviews.
The Worf Effect: A way of noting a more powerful enemy's strength is his or her ability to severely injure Zelgadis, who is normally invulnerable to mundane attacks. This also tends to come into play to display the extent of Lina's magical power, namely during the battle with Gaav and her usage of the Ragna Blade spell against Kanzel in the anime.
Would Hit a Girl: Has no qualms whatsoever.
You Gotta Have Purple Hair: Has light purple hair, and a flashback in the fifth season notes that he had it as a human; however, some sources say that his human hair is actually brown.