Zaen Kalystir huddles in a lit alcove

Finding Varsoon
1. Head to Zaen Kalystir (50, 0, -175) in Vermin's Snye. Go upstairs, down the water tunnel and then right.
2. First head to visit the Tomb of Varsoon in North West Antonica. It is on the Forbidden Island (375, -20, -675).
3. Return to Zaen Kalystir and he will send you to find the hidden entrance to Varsoon's Lair.
4. Head to Thundering Steppes and to the South East corner. Follow the zone wall very closely avoiding as many mobs as possible. Glimmering Goblins are guarding the entrance and it is sometimes possible to enter and get the ding without aggroing. (I died about 3 times trying to get the ding and on my last try I did it without any aggro at all)
5. Head back to Zaen Kalystir to update your quest.