Putrid Cyst

This one is simple enough really,
just kill Afflicted "Whatevers."
Which are EVERYWHERE all over Cantha Prime (well, the ones u need to get Cysts to drop from are on the Canthan mainland, the level 20 (26 in HM) ones)

Here are the GW Wiki notes:
Enter from Sunjiang District (outpost). Clear the southern area, then head northwest up to the water. Head back east and finish in the southwest.
Here is someone complaining on GW Wiki about the drop rate for Putrid Cysts:
These things are ridiculously hard to get. I killed 100 afflicted with 3 heros and got 0. A tip is to bring a tank, healer and minion master hero with you, along with a henchmen healer. This way putrid cysts will drop more often than with a full party. Doing this, i got 3 within 5 minutes of searching, but another 10 minutes passed and i got none.
And here is someone responding to the complainer on GW Wiki:
Must just be your luck mate, I get them pretty regularly in Shenzun Tunnels. Usually use SoS, Communing Xandra, AoTL MM and Resto Razah.
And here is me, not on GW Wiki:
Omg, stfu ffs and just go out anywhere in Cantha, the Echovald Forest, the Jade Sea or with the Winds of Change (part 1) storyline active and just kill some of the Afflicted assholes. Sunjiang District however, IS a good place to start as noted.

And that's really all I have to tell you today.  
Good luck.
Happy hunting.
blah-blah-blah blah blah  
Atty

Oh, btw, Nick wont appear if you have WoC active so make sure u do it on a toon who has either never started WoC, has finished WoC or has the Memories of Purity quest.
And just an FYI, u cant get the Memories of Purity quest (from the Herald of Purity in KC) until the particular toon in question who has started WoC has done about 1/2 of WoC pt1