Here is the full list of all 31 Thy Sword achievements.
Get hit by your own arrow.
Gamble away all your money.
Get killed by an explosive barrel.
Kill the Spider Queen.
Chop 50 heads enemies in one game.
Get the key to a chest.
Headchop an enemy.
Finish the tutorial.
Unlock the Viking.
Unlock the Paladin.
Unlock the Rogue.
Bet 100 gold and get 21.
Collect 1000 gold.
Save the witch.
Finish the game with the Barbarian.
Finish the game with the Valkyrie.
Finish the game with the Viking.
Finish the game with the Paladin.
Finish the game with the Rogue.
Headchop the other player in co-op mode.
Kill a flying enemy with an arrow.
Find the secret gate to the loot room.
Die for the 100th time.
Finish the game.
Finish the game in hero mode.
Kill the Dragon Lord.
Kill the Sorcerer of Thorn.
Kill the Lich King & Queen.
Kill the Lurking Horror.
Gain all five crystals.