The Elder Scrolls: Tamriel

You call out into the sky with a Voice known only to dragons. If you are outdoors and in a location accessible by flight, a powerful dragon ally hears your call and chooses whether to respond. If the dragon chooses to answer, it arrives 1d4 rounds later, landing dramatically in an open space within 60 feet. The dragon fights alongside you for up to 5 minutes, obeying no more than three spoken commands and prioritizing your survival. It will leave if it drops below half HP, if you break its trust, or if you dishonor the pact between you.