Here is the full list of all 28 Hnefatafl achievements.
Win a game against the computer as the white player.
Win a game against the computer as the black player.
As black blockade one corner.
Block two corners while playing as black.
Block three corners while playing as black.
Block all four corners while playing as black.
As the black player build a cordon.
Defeat all black pieces in an online game.
Win without losing a single piece in an online game.
Win with only the king left as white or with only two pieces left as black in an online game.
Capture the king in an online game.
Capture the king while he is on the throne in an online game.
Capture the king next to a corner piece in an online game.
Capture any piece next to a corner in an online game.
Escape with the king in an online game.
Finish an online game of Alea Evangelii.
Capture two pieces at once in an online game.
Capture three pieces at once in an online game.
As the black player capture the king and another piece at the same time.
Form a shieldwall and capture multiple enemies at once.
Capture an enemy piece by jumping over it with your knight.
Foteviken Tablut: Capture a black piece that is still in a basecamp.
Create your own variant.
Win as white player by escaping through an exit fort in an online game.
Join your first tournament.
Finish an online match using the quick mode.
Win your first online match.
Win a Berserk Hnefatafl online match.