Alexstrasza the Life-Binder, Aspect of the red dragonflight, is the guardian of all life in the world of Azeroth. One of five great dragons chosen by the titans to be empowered with a portion of the Pantheon’s power and rule over her flight while they watch over Azeroth and its inhabitants.
Eonar, the Titan patron of all life, gave a portion of her power to the red leviathan, Alexstrasza. From that point onward she would work to safeguard all living creatures within the world. Due to her supreme wisdom and limitless compassion for all living things, Alexstrasza was crowned the Dragonqueen and given dominion over her kind.
This is my gift: compassion for all living things. A drive to protect and nurture them. And the ability to heal that which others cannot, birth what others may not, and love even the unlovable–who surely need such grace more than any other souls.
– Blessing of the Red Aspect, given by Eonar
Alexstrasza appears normally on the top tier of the Wyrmrest Temple in Dragonblight in a form resembling an unnaturaly tall female high elf or blood elf with pink skin, amber eyes and horns. During the Wrath of the Lich King, many members of the red flight, including Alexstrasza and her prime consort, had led the Wyrmrest Accord, an alliance of the remaining four dragonflights defending the temple against the blue dragonflight and its Aspect, Malygos. The undead Scourge had laid siege to the surrounding five dragonshrines in an effort to raise terrifying new variations of undead dragons. To arrest these invasions, Alexstrasza had begun recruiting heroes to aid Ceristrasz and Vargastrasz in the Ruby Dragonshrines defense against the Lich King.
Alexstrasza also appears in her draconic form at Angrathar the Wrathgate after the completion of Return to Angrathar and in the Eye of Eternity raid in the Nexus, where she and her children will aid players in slaying the Spell-Weaver.
With the rise of Deathwing during World of Warcraft: Cataclysm, Alexstrasza has taken a very active role in defending Azeroth against the Aspect of Death, eventually ordering her entire dragonflight to war against the Black Dragonflight. She and her red dragonflight are featured heavily in the Twilight Highlands where they fight against the Twilight’s Hammer clan and struggle to breach Grim Batol. Alexstrasza herself battles Deathwing above Grim Batol during the Battle of Life and Death quest. Though Deathwing is gravely wounded, so too is Alexstrasza. She is taken to Wyrmrest Temple to recover from her injuries, but the weakening of Deathwing bought the mortal races time to prepare a final assault against him.
The reds are utterly loyal to their Aspect, Alexstrasza, who along with her consorts such as Tyranastrasz and Korialstrasz, are treated with great respect by the reds and the other flights. The reds are typically the only dragons mortals are likely to encounter, with the exception of the druidic allies of the greens. Like all dragons, they take their charges seriously and usually operate in secret, keeping tabs on important beings, organizations, and places, such as Cenarius, Dalaran, and the Scourge. As a result, the red dragonflight’s agents are often away, spreading themselves throughout Azeroth, and using their powers to disguise themselves as members of the mortal races, such as humans or elves. Like all dragons, the reds have the ability to create illusions on themselves and others. Often the dragons have mortals, dragonsworn, working on gathering information or doing other related errands.
All this is done to maintain harmony and the prosperity of life, the task entrusted to them. Due to Alexstrasza’s influence, the red dragonflight see themselves as custodians and defenders of life on Azeroth. Red dragons understand the secrets of life, and in turn those of death, like none others do, and have been granted great power over both. They are capable of rejuvenating and draining life, as well as performing a form of necromancy, though only as a last resort, as they are not fond of doing so. The breath of red dragons burns but also rejuvenates, and whenever a red dragon walks or breathes upon the soil, the earth is renewed.
While red dragons are the protectors of life, they will not hesitate to kill a creature if its actions endanger other lives. Many members of the red flight still remain distrustful towards mortals, especially the orcs, citing they have brought only danger and death to the world. Generally, though, red dragons are friendly to humans, elves, and their other traditional allies; for the most part, it is the representatives of the flight near Grim Batol who acted strangely hostile to any outsiders. The drake Axtroz and the dragonspawn located there will attack adventurers on sight.
Adult red dragons most often have names ending in “strasz” for males, or “strasza” for females. When taking humanoid form red dragons most often choose human, high elven, or blood elven forms.
Info taken from WoWWiki
I found the following from ‘Thrall: Twilight of the Aspects’ novel particularly sad…
After the cataclysm, the dragons convened upon Wyrmrest Temple to have their first meeting with the blue dragonflight since the death of Malygos. Korialstrasz, not particularly liked by many of the blues, specifically Arygos, chose to stay behind and watch his newest clutch of eggs in the Ruby Sanctum. As Alexstrasza traveled to the meeting above, Korialstrasz discovered the Twilight Hammer within the sanctum, casting dark spells on the eggs. Confronting them, he discovered that their spells had mutated the hatchlings, transforming them into deformed chromatic dragons. When he touched a mutated egg, the infection passed on to him. It was then revealed to him that not only was the entire clutch of eggs infected, but every flight’s eggs, in each of their sanctums. Half-mutated into a Chromatic dragon but thinking of his beloved Queen one last time, Korialstrasz summoned every ounce of his power and exploded the sanctum outward, destroying a good chunk of Wyrmrest Temple, and utterly obliterating himself and the sanctums. Along with the sanctums fell the thousands of corrupted eggs. While his death and apparent betrayal was a shock to the other dragonflights, Alexstrasza suffered the most. In sadness bordering on madness, she shattered the Wyrmrest Accord and fled to the center of Desolace, where she sat waiting for death. Thrall attempted to rouse her from her depression but could not.
Later, during a battle above Wyrmrest Temple, Thrall had a near-death experience after falling from extraordinary heights. In his vision, among other things he saw the truth behind Korialstrasz’s actions. When the battle had ended, Thrall brought the news to Alexstrasza, who rejoined the fight with renewed purpose to not let her love’s sacrifice be in vain.
Taken from Wowpedia
The Red Drake mount is available at Exalted reputation with Wyrmrest Accord. Prior to The Shattering, this whelpling dropped from the Red Whelp, Flamesnorting Whelp, and Crimson Whelp. These creatures have since been removed. As of Patch 4.0.3, the Tiny Crimson Whelpling is now a zone drop from the Wetlands.