Margrid The Sly?

Right now im playing Nightfall Campaing and i can't do the Pogahn Passage mission because i don't have Margrid The Sly. How can i get the hero Margrid The Sly?
PS: I've searched on wiki but that doesn't help me!

If you don't have Margrid, that means one of the following:
1) you have Master of Whispers
2) you're not far enough through the game

Therefore, you need to do one of the following:
1a) beat the game, which allows you to pick up all missed heroes including Margrid to do the mission
1b) join up with somebody who does have Margrid and do the mission with them
2) advance farther to where you can choose to take either Margrid and Master of Whispers

Yes i have Master Of Whispers...so the only way to get Margrid is beating the game...cool! Thanks!

Remember to talk to her at the very end to get the quest.