Here is the full list of all 34 Greymarsh achievements.
Gained a stranger's trust
Lived to see morning
Defeated the highwaymen
Entered Greymarsh
Got acquainted with Halodorus
Gained access to The Pit
Defeated the Wasp man
Defeated everyone in The Pit
Unlocked three areas
Solved three riddles
Gained access to The Arena
Defeated the less tough opponents
Defeated the Garnathian goblins
Defeated the barrel
Defeated the wyrmling
Became the owner of a spear
Defeated the spiders
Defeated the prince
Unlocked the sewer entrance
Defeated the mutant in the dungeon
Found the southern sewer exit
Found the entrance to the crypt
Defeated the crypt dweller
Unlocked all areas
Defeated the guard officer
Defeated the magicians
Defeated the general
Defeated king Hraga
Made an important choice
Finished the game in 1000 turns or less
Finished the game in 750 turns or less
Calmed and shoed the horse
Beat the juggler at his own game
Arranged the historian's books perfectly