Again, your main quest objective here is to assassinate the infiltrating homunculi. The full breakdown of objectives is as follows:
Your Exodar mark is Ardaan the Solemn.
From Dalaran (Legion), take the portal to Orgrimmar, then to Hyjal. From there, fly to Rut’theran Village on Teldrassil (it’s at the base of the tree). Then hop on the ship that pulls into the western dock (Elune’s Blessing).
Ardaan and his bodyguard, a Crystalforged Demolisher, walk around the city in a loop. Distract or Blind the Crystalforged Demolisher so it will separate it from Ardaan. Otherwise, it will one-shot you if decide to attack without doing so.
The loop path they walk is depicted below:
Your Darnassus mark is Taylenne Sweetsong.
Take the ship back from the Exodar. You can get into Darnassus one of two ways -- through the glowing pink portal at the top of the hill, or by flying up the tree to the top (it’s a really tall tree).
Taylenne is located just under the words ‘Warrior’s Terrace’ on the area map. She will make rounds around the party tables, mingling with the other partygoers. There are Elites at the party that hit like trucks.
The best spot to take her out is over by the buffet table. Some of the Elites will make their way to the table for refreshments, so be aware of this. Take out the non-Elites when there’s a window, and wait for your opportunity to take out the mark.
Beware! There is a stealth-detecting guard that pats along the path just south of the party. So keep your eyes peeled or you're gonna get spotted.
Your Ironforge mark is Corin Twinbellows.
To get to him, you can take the portal from Orgrimmar to the Twilight Highlands, then fly to Ironforge.
Corin is located in the High Seat, where the Council of Three Hammers resides. In fact, he’s right past the giant doorway on the right. Flying to the Gates of Ironforge, then finding a safe spot to land and stealth is probably the best way to go.
He is stationary but has a buff that reduces the damage he takes by 99%. Pickpocket a key from him, then Sap and use that key to take his armor off to get rid of the buff. Once you do this, he will run away from you and cast Cry For Help to call for guards. So make sure to interrupt him and take him out quickly.
Your Stormwind mark is Auctioneer Jaxon.
The fastest way would be to hop on the Deeprun Tram from Ironforge. You could also take the portal to Twilight Highlands again and fly to Stormwind.
Jaxon is located in the Trade District Auction House and behind the far right podium. The only thing you really have to worry about here is other players who are waiting to kill you. So you'll want to kill Jaxon quickly and then Vanish as fast as possible.
Once all the marks are dead, head back to Lillian and reap your rewards!
That wraps up our guide for completing the Hiding in Plain Sight quest. If you need more tips for grinding through Azeroth, check out the rest of our WoW guides!