when you kill Phara Dar, because NO ONE... REPEAT >NO ONE< Has beaten Phara Dar. Also, this supposed gate you've heard about is B.S., Veeshan isn't in the game, she's larger than the entire planet of Norrath. This is how Rumors get started.
In Veeshan's Peak: Phara Dar is the top dragon in Veeshan's Peak and comes along with an AE stun and DD. She spawns adds called Protector of Phara Dar at intervals based on her current hit-point %.
In Field of Scale: Phara Dar is a quest NPC.