Thaero was an elf who lived in the latter days of the First Age, but seemed to have vague memories of an earlier time and place. The earlier time seems to be the time of the Elder Gods and the place was perhaps the Fair Lands.

Thaero remembered living in a woodland area with a bear as his companion. Thaero quickly became skilled at script magic and used it to attempt to learn the true magical names of animals so that he might enlist their aid in his various quests. First among these quests was to assist the Realm of Azmar. Thaero visited Azmar Island during the Ogre Wars, saw their desperate plight and offered to assist. For this, he was granted the title High Ranger of Azmar by the Warlord Karleg of Azmar. Karleg also gave Thaero his sword. Thaero brought the legendary elf wizard Allort to Azmar and got him to agree to assist Azmar as well. Thaero was then sent on a new quest by the Warlord Karleg to find a new home for the people of Azmar so that they could flee Azmar Island and end the Ogre Wars. Thaero first recommended Sheep Island as a refuge and this suggestion was partly responsible for the annexation and colonization of Sheep Island by the Realm of Azmar, though this happened while Thaero was away traveling.

During his travels to seek a haven for the dwarves and gnomes of Azmar, Thaero was given a vision by Tronor of a lush woodland.  When the vision was over, Thaero was surprised to find that many years had passed.

Thaero was surprising to discover that in the years that had passed, The Realm of Stondar had been established, the Battle of Ogre Island had been fought, and the Warlord Karleg of Azmar had been slain by a dragon. Learning of this, Thaero determined to set reach Azmar Island to offer to assist the new ruler there, Prince Yarl of Azmar.

While in Stondar, Thaero was shocked to see an elf being chased by a Stondarian dwarf warrior. The chase had ended at Orveka where the elf had climbed the roof of one of the gnome buildings and the dwarf was unable to get up. Others had gathered around to see this and were talking of attacking the dwarf. Thaero instead asked what had started the fracas. The elf admitted having hit the dwarf first. Thaero then chastized the elf for breaking the peace and threatening to destroy the efforts of himself and the elf wizard Allort to build good relations between elves and the dwarves of Stondor. The elf then hid from the dwarf and the dwarf gave up and left.

One of those who witnessed this event was an elf maiden named Valindra. When she learned of Thaero's desire to go to Azmar Island, she loaned him a magic portal ring that allowed him to travel there by magic.

Reaching Azmar Island, Thaero met Prince Yarl of Azmar. Prince Yarl confirmed Thaero's title of High Ranger of Azmar and again asked his aid, now not only to seek out new lands, but also as an advisor to the prince. Thaero's first advice regarded Sheep Island which had been lost by Azmar to Ogre Raiders in the Ogre Wars. Thaero proposed to retake it.

Yarl did not take immediate action to recapture Sheep Island. Thaero made an unsuccessful effort to enlist the aid of Prince Noreg of Stondar in recapturing Sheep Island. Then, Thaero joined the efforts of Lord Garon of Sheep Island to form his own army and recapture the island. Thaero fought at the Battle of Sheep Island as part of Lord Garon's Army and was rewarded with a land grant on Sheep Island.

Around this time, Thaero developed his technique for taming wolves and tamed a wolf he found on Worfin Island and named it Kyron. Kryon fought in the first part of the Battle of Sheep Island.