Forerunner: The Second Venture — Andre Norton

Simsa, the beggar whose mind held the ancient legacy of the Forerunners, had escaped her claw-and-fang life in the Burrows, with the off-planet Rangers. But the Rangers wanted her in captivity for study by historians.

So Simsa and Zass, her winged hunting zorsal, escaped again, taking a stolen lifeboat to an unknown world. A desert where shapeshifting creatures lurked beneath the sand, where Zass and Simsa's hunting skills, psychic powers, and strange link to the Elder One in Simsa's mind were their only survival weapons.

Then Thom, the Ranger who saved -- and perhaps betrayed -- Simsa, crashed on the planet. Together, they realized that a mysterious, mind-threatening and possibly monstrous power had found them....

And only the Elder One could help.