Here is the full list of all 29 Rune Classic achievements.
Complete the game (any difficulty).
Complete the game on Medium difficulty.
Complete the game on Hard difficulty.
Defeat Sark Conrack.
Become Sark Ragnar.
Obtain all the Runes of Health
Get all the weapons in the game.
Defeat the Dark Dwarf.
Defeat the Trial Pit Beast.
Drink 25 Steins of Mead
Kill 250 enemies.
Make your way through Hel's Chamber
Kill 100 enemies.
Eat 25 Lizards.
Avoid the Dealy Dangler Fish.
Kill 25 Enemies.
Behead 100 opponents in multiplayer.
Get "First Blood" 10 times
Beat an opponent to death with a severed limb.
Defeat an enemy by setting them on fire.
Get beheaded in multiplayer.
Behead 25 opponents in multiplayer
Kill 100 enemies while Berzerk.
Behead 10 opponents in multiplayer.
Kill 100 opponents in multiplayer.
Kill 50 opponents in multiplayer.
Kill 25 enemies while Berzerk.
Get a 10 player kill spree in multiplayer.
Kill 10 opponents in multiplayer.