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