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.
Defeat the Dark Dwarf.
Drink 25 Steins of Mead
Defeat the Trial Pit Beast.
Kill 250 enemies.
Obtain all the Runes of Health
Make your way through Hel's Chamber
Defeat an enemy by setting them on fire.
Kill 100 enemies.
Avoid the Dealy Dangler Fish.
Eat 25 Lizards.
Kill 25 Enemies.
Get beheaded in multiplayer.
Behead 100 opponents in multiplayer.
Get "First Blood" 10 times
Kill 100 enemies while Berzerk.
Kill 100 opponents in multiplayer.
Kill 25 enemies while Berzerk.
Kill 50 opponents in multiplayer.
Behead 25 opponents in multiplayer
Behead 10 opponents in multiplayer.
Get a 10 player kill spree in multiplayer.
Kill 10 opponents in multiplayer.
Beat an opponent to death with a severed limb.
Get all the weapons in the game.