Zilant or Ajdaha is a legendary dragon in Turkic (Tatar) and Russian mythology which is mentioned in legends about the foundation of Kazan.
TEnglish transcription of Russian Зилант, itself a rendering of Tatar yılan (Cyrillic: елан). The Tatars themselves, on the other hand, frequently refer to this creature with the Persian word Ajdaha (Dragon) or Ajdaha-yılan (Dragon-snake). There is also speculations that Zilant's origination was not from the White Snake, but the Falcon (Börket), an image similar to Zilant from an earlier epoch.
Zilant is often confused with Aq Yilan (White Snake), which is the king of snakes as well as the medieval cockatrice.
Early Russian images represent Zilant with one head, four chicken legs, a bird's body and a snake tail. The modern perception of Zilant among citizens of Kazan today is strongly influenced by Western culture and many modern citizens imagine Zilant to be a more classically Western wyvern or dragon as depicted in films.
Yilan or Sahmara advised and helped epic heroes, batirlar, often by giving them gifts. As regards his *beneficial influence on humans, the White Snake is similar to the Chinese dragon. According to Idel-Ural beliefs, any snake that survives for 100 years turns into Ajdaha dragon. For Kazan Russians, Zilant had negative connotations, as it was represented as a Slavic dragon rather than a snake.
The popular historian Lev Gumilyov pointed out in his Ancient Turks that the Kypchaks, one of the ancestors of modern Tatars, came from the Zheliang Valley in the Altay Mountains. In his opinion, the nearby Zheliang Mountain and Zheliang settlement were named after Zilant the White Snake. After the 16th century Russians acquired this legend from Tatars. Hollander Carlus Allard noted that The Cæsar of Tatars once had two flags and Zilant was pictured on one of them, most likely the flag of Kazan.
These flying snakes were also known in Bolghar, Suar, Bilär and the other cities of Volga Bulgaria. For the most part, these snakes were benevolent. However, in the boundary fortresses of Kazan, Alabuga and Cükätaw, legends about flying monsters flourished. One particular fortress on the Shishma River was known as Yilantaw, later russified as Yelantovo. Many scholars believe that Zilant, like other flying snakes, symbolized the evil rulers of the neighboring pagan peoples. The legendary burning of the snakes may symbolize the victory of Islam over paganism. Sceptics say that the Bulgars purposefully spread those legends in the border regions in order to dismay their neighbors.
- A beautiful damsel married a resident of Old Kazan. She had to get water from the Qazansu River and complained to the local khan that his capital was poorly situated. She advised him to move the city to the neighborhood of Zilantaw Hill, and the khan agreed. However, the hill was infested with numerous snakes which were "stout as a log". Their leader was a giant two-headed snake, i.e., Zilant. One head ate only grass, while the other swallowed virgins and youths. A wizard advised the khan to build a straw and wood near the hill. In spring, the snakes came out from their winter burrows and crept into the pile of straw. A knight errant was sent out to set the pile of straw on fire, burning out the snakes. They were deadly even in death, "killing people and horses with their stink". However, the gigantic two-headed snake-dragon escaped to the Qaban lakes. According to the story he still lives in the waters of the lake and, from time to time, takes vengeance on the citizens. According to other stories, the giant snake was transformed into Diü, a spirit who founded the underwater kingdom of the lake.
- It is also said that say that Zilant did not escape to the lake but instead tried get revenge upon the knight, who by that time had ridden some 50 çaqrim  away from Kazan. During the fight that followed, Zilant cut the hero into six parts. The knight, however, had managed to stab the dragon with his poisoned pike, and Zilant eventually died.
- There is also a legend about Zilant's return to Zilantaw. They say that Zilant re-established himself in a big cave near the hill. The dragon would occasionally fly over the panic-stricken city and drink water from the Black Lake. At first the people of the city people paid tribute to him, but later they managed to kill him with a wizard's help.
- According to one legend, when Bulgars came to found the town of Bilär, they discovered a big snake. They decided to kill it, but the snake begged for peace and pleaded with Allah to give her wings. Once she had her wings the snake flew away from Bilär.
- Another great snake was said to live in a pagan tower temple at Alabuga. Although the Bulgars adopted Islam as early as the 10th century, the snake survived until the time of Tamerlane's invasion after which it disappeared.