Zaetar

Zaetar was a keeper of the grove and the eldest son of Cenarius. After mating with Princess Theradras, he became the father of the centaur race, but was soon killed by his barbaric children.

Birth of the centaur
Zaetar was born the son of Cenarius and brother of Remulos. Where Remulos was strong and beautiful, Zaetar was very cunning and slight of build. Like his father, Zaetar walked the physical world in the form of a majestic half-stag, with vines and leaves encircling his limbs and antlers. Wherever he walked, dozens of saplings would sprout and—over time—grow into lush groves. While the two brothers were respected equally, Zaetar always felt as if he could never compare to the glory and attention he thought Remulos had. When Remulos' children—Celebras and his dryad sisters—were born, a jealous Zaetar set out to outdo his brother.

When the earth elemental Princess Theradras was roused from her slumber by the tauren, she drained the lands of Mashan'she of life to restore her powers. The loss of so much life sent ripples through the Emerald Dream, and Zaetar emerged to investigate, eventually discovering Theradras in heir lair. Despite having set out to imprison the strange creature responsible for draining Mashan'she, Zaetar soon became enticed by the elemental's stolen life energies and grew enchanted with her beauty. Theradras realized the influence she had over the keeper, and—as she found Zaetar beautiful as well—claimed that together the two could restore the land to its former beauty. Despite knowing that it was against nature and despite the warnings of Remulos, Zaetar became Theradras' mate, and from their forbidden union, the barbaric centaur were born. The first centaur were allegedly Gelk, Kolk, Magra, Maraudos, and Veng, who became the first five khans. Upon seeing his children, Zaetar immediately realized his sin. Despite trying to connect with his offspring, the centaur saw the disgust in their father's eyes and brutally murdered him. Theradras harshly chastised the centaur, who—upon realizing that they had wounded their beloved mother—promised to honor Zaetar's memory. Theradras entombed her lover's spirit in her lair, which the centaur named Maraudon and came to regard as holy ground.

In Maraudon, Zaetar's Spirit is seeking for help to slay Theradras and free his spirit so that he may restore Desolace to a place of verdant life and promise, as Cenarius would want. Some believe that Theradras, in her grief, trapped Zaetar's spirit within the winding cavern - used its energies for some malign purpose.

Stormrage
Broll Bearmantle is lead to Zaetar while in the Emerald Dream. Zaetar was leading a group in battling the Emerald Nightmare. He is described as having a greener tint than Remulos, and a faintly longer face that bore in it a constant sadness.

Cataclysm
Though Theradras was considered deceased by the lore, Zaetar's spirit gives new quests that require to kill Lord Vyletongue, Noxxion and Razorlash. His ultimate goal then is Theradras herself in order to free himself. This may be due to the fact that Maraudon was not changed to reflect the storyline.

In the RPG
The product of Zaetar and Theradras' union were five tribes of centaur (Magram, Kolkar, Galak, Gelkis and Maraudine), twisted mockeries of the beauty of the dryads and keepers of the grove. According to the story, the first act of the jealous and evil centaur was to kill their father. Fearing Cenarius' wrath upon her children, Theradras spirited Zaetar's remains, and his soul, away to be with her in Maraudon.

As he is the eldest son of Cenarius he is likely the one known as "the keeper of the grove" in the night elven legend that speaks of three oldest offspring of Cenarius, his sister "the dryad" and his bastard brother, "the centaur" (the first of those races). Keeper Remulos is one of his younger brothers not mentioned in the legend. Zaetar's nephew, Celebras, the son of Remulos, attempted to rescue Zaetar's spirit from Maraudon, but became corrupted himself by Theradras' magic, and still resides there with his dryads.

As he only fathered five tribes according to World of Warcraft and Lands of Mystery, he is not likely the progenitor of the Krenka, the Marauders, the Stonetalon tribe, or Eastern Kingdom centaur tribes. Instead, those centaur were likely were the sons of Zaetar's bastardized brother mentioned in night elven legend, "the centaur".

Speculation
Alternatively, some believe that the two legends (this one and the night elf legend) are one and the same, in which the son called "the centaur" may, in fact, be Zaetar. This is because they share many things, such as their fall from grace due to jealousy. This would mean that "the centaur"'s children were the same as Zaetar's. Those also believe that the Krenka, Marauder, Stonetalon, and Eastern Kingdom centaur may have simply broken away from the five main tribes in the countless centuries since their creation, as the five tribes remaining unbroken for well over ten thousand years may seem unrealistic.

However, this would ignore most of the traits, and history attributed to "the centaur". Zaetar appears to neither be a bastard, nor does he have the centaur's personality traits. He does not have the same hatred of his siblings as "the centaur". Zaetar was not cursed by his father either (stripped of his beauty to appear as current centaurs), nor did Zaetar swear a blood feud on all creatures of the world. These discrepancies could be explained as exaggerations added as the story was retold over the years.