When Luclin blew up we were told they pretty much all died. The few Vah Shir adventurers who happened to be on Norrath when teleportation was cut off assimilated themselves into the Kerra tribes, bred with them, and then died off from old age themselves. So how does the lore explain how some of them survived and they are now a playable race?
It's a long story that ends the entire Kerafyrm / Age's End Prophecy story that the game's story has been building up to the Tears of Veeshan storyline. Long story short: a magic artifact that greatly amplifies any type of magic is used to focus Chronomancy to put the remaining majority of Luclin back together, completely undoing its destruction. The Vah Shir and rest of the inhabitants on Luclin are now back to life with barely any knowledge of how much time has actually passed (though the undead and other spirits had to suffer through the 500 years since then, so they caught the Vah Shir up to speed on how much time has passed.) The Blood of Luclin storyline goes on to explain that Luclin itself experienced a strange cataclysm that resulted in massive crystaline formations jutting out of the landscape. A result of the Dresolisk Crystal that blew up the Nexus being detonated -- but the time magic put Luclin back together at the very moment that the crystal was detonated but before the explosion could actually happen. Luclin's destruction has been undone with time magic.
