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