Defeated the Varterral on Hard or Nightmare difficulty ("Witch Hunt" Downloadable Content)
Once you get to the Dragonbone Wastes you will come in an area, after a bit before a big area where the game auto saves there will be a boss. Make sure you set the difficulty on either Hard or Nightmare.
The boss itself can be seen as a giant grasshopper. It has attacks that does moderate area damage and stuns/slows characters. It tend to disappear through the fight and call for 2 dragons each time. These are easily killed. Just continue hammering the boss and he should go down very fast.
(This boss is very easy on hard mode, nothing compared to the Harvester from Golems of Amgarrak dlc). You should not have any problems with this boss.
Completed "Witch Hunt" ("Witch Hunt" Downloadable Content)
Simple enough, finish the DLC.
A Time of Wood and Stone
Gathered the lost lore of Cadash Thaig ("Witch Hunt" Downloadable Content)
For this one you have to gather 4 old documents items from inside Cadash Thaig.
Through the Looking Glass
Completed the scrying ritual ("Witch Hunt" Downloadable Content)
Story related trophy. You will get this after you got both the glass shard and 4 of the lights. The Ritual is performed right after you got both at a nearby spot and the trophy will popup after that.