Star Dragon

The oldest and most powerful of Ulthuan's Dragons are referred to as Star Dragons, for they are truly as ancient as the very stars of the firmament. While any dragon can savage an entire regiment of warriors, tear a Manticore apart or rip the head off of a Wyvern, a Star Dragon is so physically powerful that it can battle against even the Greater Daemons of Chaos and prevail.

Source

 * Warhammer Armies: High Elves (8th Edition) -- p. 39