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